Linksfahrer

Although somebody will be running more power its generally accepted on here that > 350bhp the 5spds are not going to last forever .
For anyone looking for power on a 2.0 WRX you first have to ask yourself a simple question do I or do I not want a 6spd gearbox.
that gives you 3 options either : sell you car and buy an STi , buy a 6spd and convert your WRX., or compromise at around 350bhp and call it a day.

Id like to use this thread to show a possible tuning path upto 350 bhp for someone looking for a good daily driver using a MY05 WRX as a starting point,
but not going with the accepted switch to find that power with an aftermarket equal length exhaust header, but instead to stay with the cast iron iconic unequal length
standard part, and keep that Subaru flat 4 burble.

I am firstly going to list out the modifications to my car that were made to get to 328.6 bhp on Momentum99 Fuel.
I have a 93mm re-bore on my 2.0 so bear in mind the 2038cc of cubic capacity / power is slightly up/over your 1995cc WRX engine.

Mods are :

Walbro 255 fuel pump
Cosworth Air filter. in Std housing
Inlet Tumbler deleted (not essential)
565cc Injectors Dark Blue from WRX06
Iridium or NGK 7s spark plugs.
SC36 Turbo ( basically ScoobyClinics Blouch Turbo with lighter vanes)
3 inch diameter 200cell Sports Cat Downpipe.
Adapted down to fit to a 2.5 inch Decat middle section and Prodrive 2,5 rear box.
( a full 3 inch system would also be good / but harder on the ear. )
Harveys "Trick" Decat Uppipe for 2.0 ltr ( not a large diameter )
STi Top mounted Intercooler from a Sti MY 04 -05 1/3+ larger than the WRX's is not essential but helpful to keep Intake temps down.
3 Port Boost controller.
Conservative map by Martyn at Plymouth Engine tune.

While the above collection of goodies will easily produce >300bhp when mapped
its advisable to take at least a Sti Brembo front disc brake conversion and some Coil-overs to keep this lot on the road.

Ok so here is the Dyno result of the above when mapped at Plymouth Engine Tuner. Brief was plenty of torque , but hold the top down, ( Its a Forged engine I want to keep a long while if I can )




The peak boost here on my gauge 1.45 bar and tailing down from 5750rpm

Ignoring for a moment the peak Bhp with its flat power from 5750 to 7000 rpm , Id like to draw attention to the torque curve and in particular the spool of the turbo (or lack of it) from 2500rpm up to 3900rpm
now although these values are by no means slouch of the day , I think that a lot can be done to improve spool by removing the restriction that i believe is holding what is an otherwise pretty good turbo (supposedly a 360bhp unit)
back from doing a better job. Now obviously it would be possible to increase boost may be 1.5 or even 1.6 bar but at some point the gains in pressure are not rewarded by gains in power because the engine can't breath.
However at low rpm you would expect more power right ? well no at low rpm the flow characteristics of the inlet/ head itself and exhaust outlet ports / headers offer a turbulence resistance which although very small does detract
from getting the flow through the engine, and the turbo is just not running fast enough to push it through. The engine at 2500rpm is running like a normally aspirated one , but at lower compression ratios not even a very good one.

Ok so what can we do , well yes raise the CR , but I have not , I built this engine with near normal CR , the extra cubic capacity from the overbore is cancelled out by some work in the chamber to deburr clean up the sharp
edges in the combustion chamber casting to help prevent pre-detonation. The head gasket is a 1.2mm one , and I can change that later if I desire.
Raising CR would give me more torque low down, and is certainly something to be considered for the daily runner but would restrict my Mappers latitude to develop more boost and timing advance for peak power.
( I'm still not a my target 350bhp ).

So here is the plan , To port the standard cast iron headers to flow the exhaust gas out easier at low and higher rpm.

I would normally do this work myself and indeed have done this type of optimisation and other head work on race minis and fast fords in the eighties , but anything on cast iron takes a lot of elbow grease and in the case
of the Subaru headers you need a long grind tool to get deep into the tight curves, so I put this work over to Plymouth engine tuner , they put it out to a trusted specialist ( Edit note I might name this later when results are in )

Here are some photo example of the porting work done on my headers. You will notice that the material is not 100% smooth but that no large lumps/constrictions are obstructing a smooth flow
this is very important. Its important to keep the header opening matched very slightly larger than the cylinder head outlet. Open it too much (to the full size of the gasket ) and you will lose power,
as turbulence occurs at the pressure drop point.


Equally making the pipes too large in diameter can cause a drop in gas speed and at low revs that equals turbo lag.
Which is another reason why some after market headers don't function well for the 2.0WRX,
leading some mappers to warn against them.






Next step is planned Mid Jan to have the headers fitted and the Remap Completed

Many would say this you don't need to do this. But I think this modification could really open up some torque and some better breathing
so it should be given a chance , Martyn says if you can do anything that can up the power at the same or lower boost then its worth doing

Placeholder Earlier SRR Power Graph 311bhp China TD05 16G / Prodrive Cat downpipe ( Torque almost identical to 328bhp run in low sub 3500rpm area) boost 1.55 Bar







TD05 16G versus SC36 alone has not made any real difference in the bottom end Torque. Torque is near identical from 2500 thru 4000rpm
Although it must be said mine is not the latest "SC36 R" Ball raced version the SC36 does not out perform the TD05 16G in this area, ( perhaps not unsurprising as it has the same size housing )
but more bhp top end flow seems possible on the SC36 , I assume that the extra 40 cc from my new 93mm overbore and some very light clean up of the combustion chambers casting imperfections
and minor blending on exhaust ports contributed to the 17bhp gain over the TD05 16G , and perhaps the SC36 (Blouch) light weight fine fins on the compressor are marginally more efficient.


These graphs are retesting power before/after fitment of the ported headers but without a map change. A slight drop since last dyno run.
I find this interesting as we can identify a slight improvement 10lb/ft in torque from 3250rpm-4250rpm,
showing in fact a shift of 200rpm to the left along the whole curve. So we can conclude header porting does improve torque on its own.

However this is not the whole story as now the mapper has a chance to exploit the gain with adjustments to the map.




So after adding just the Ported headers and another Engine-tuner remap to reap the power from improved breathing, we gained 15 bhp and held it longer across the rev band.
In addition we see 25lb/ft more torque in the basement 3500-4500 range and a torque improvement is held across the curve still giving 250 lb/ft at 7000rpm .

Mappers note . "This time around the car took and held quiet a bit more timing into the top of the rev band.
this can be attributed in part to the better breathing of the headers but is also explained by the 8.0:1 CR"

So What's next ?

Obviously we missed the headline 350bhp on this by 7 bhp and although we are limited by the 1.55bar maximum scale of the EcuTek std controller;
The turbo could perhaps do a tad more, but its getting to its top area of efficiency ,
Martyn mentioned for reliability its not worth putting more boost into a little turbo , and in the end he did not need more than 1.45 bar.

To do more here: To help the low end torque, a possibility exists to increase compression ratio by going from the existing 1.2mm down to a 0.6mm head gasket,
Going maybe a CR >8.5 ;1 this perhaps could be tolerated on the 99 Octane but another remap is required and by doing so this might cost timing advance and reduce top end / width in the power band,
350bhp might well be found with more low end torque , ( and that's tempting in the NA ,3000rpm range ) but you could not hold the bhp and the torque as flat or for as long as before.
And of course the parts /labour cost, its over £1000 to do that work, Therefore I can only advise everyone to do the 8.5:1 CR and or a Stroker new build to help out in the sub 3000 rpm area.

Martyn's next tuning step suggestion for bigger torque / 20-30bhp would be to go with AVCS heads and a loom adapter,
nice to have ,but If I did this t would put me well into the disintegrating gearbox >360bhp territory.

Other things to consider at time of an engine build / tuning mods:

Go for the 1mm Longer Connecting rods to reach a full 2.1 ltr capacity which looks best for extra torque and bhp. (no surprise if you look at the 2.5ltr guys torque curves)
or also for track work do a Full Decat exhaust similar 2.1 spec ( per MalcolmB result below ) that gave 350.1 bhp and excellent bottom end torque.
certainly this looks helpful in the 6500rpm-7500rpm area , keeping the Bhp curve flatter. Which is very useful on the track if you don't wish to change up another gear prior to
braking for the next corner.

I console myself at this point, and think this increased capacity point is underlined now,
If I had used 3% more cubic capacity to the full 2.1ltr , then in theory versus my build 343bhp *103/100 = 353 bhp
I would have matched MalcomB / later Henriks old car.

I can also discount for my daily driver purposes the "need" for RCM headers or a Full Decat , I conclude the Prodrive 2.5 rear box on a 3 inch 200cell cat are also not a significant restriction at the WRX 350bhp level.
and confirming there is not substitution for cubic capacity and higher compression ratios ( if you can run it on the fuel you have). Removing the 2,5 rear exhaust section /back box in favour of a 3 inch
remain the only simple bolt on that might bring a few lb/ft or bhp perhaps the one that finally heaves me over the 350 bhp ? I suppose I can try this without a remap and Dyno retest at a later date,
I'm sort of kicking myself that I did not go for a 1mm longer rod set and a 8.5:1 CR when I made my build on the WRX, But for everyone else I hope this has been a useful exercise.
Despite the presence of a turbo , you really need to consider both higher CR and higher cubic capacity for pickup performance in the NA area. Something that our long geared 5spd are in desperate need.

Driving the car today I do notice the extra performance that Plymouth Engine tuner have tickled out for me, and I wish to thank them for throwing in the clamps exhaust wrapping FOC.

hedgecutter

iTrader: (5)

Excellent thread. This is the route I'm thinking of following on my spec C, because I want to keep the driveability of the standard twinscroll. I was considering porting as much as is possible, even some head work if worth it, and some enhanced heat management. I've read of numerous twinscroll owners who have chased bhp figures, only to lose that driveability in reality. Do you think I'm barking up the wrong tree?

1509joe

iTrader: (2)

Don't touch it not really enough material to work with. One slip could end up a very expensive mistake
The standard TS manifolds are good to 500ish.

hedgecutter

iTrader: (5)

I appreciate porting can make things worse if done badly, but how does their peak power capacity relate to how they flow, eg for spool?

1509joe

iTrader: (2)

You can gain from head work but as above as far as the headers are concerned.

Tidgy

have to say this is why i prefer the 2.5 over the 2.0. My type r was 2.5 6 speed conversion and was knocking on 450ftlb at 3750 rpm and hit 398bhp peak. Bearing in mind that was also on a front mount.



p.s. this isn't knocking your result, its purely a comment about 2.0.

scoobaholic

Quality thread! Looking forward to the updates. I‘m thinking going a similar route on my 2l sti. 350hp seems a good compromise between power and driveabilty regardless of the gearbox (at least for the UEL burble fans).

Linksfahrer

Primarily the idea is only to prevent turbulence at the lower gas speeds / gas volume , not to "open up" the full diameter of the pipe
this is also what Harvey's trick uppipes work towards , you don't take the largest diameter he has for a WRX you are aiming at just 350Bhp .
unless you are looking for big numbers. If your Spec C has little thickness of material to grind then you might well do damage, but whatever the thickness , if you just take the
rough protruding imperfections out that cannot hurt. But don't expect that doing this will gain you much in peak power you probably won't see much difference.

The idea is to get the turbo spinning , quicker at lower gas flow. The gas speed is what matters most , he only other ways I know to achieve the initial spool is to make the inertia of the
wheel less , the SC36 billlet is supposed to have 1/3 thinner/lighter material , or of course to reduce bearing resist ,introducing more advanced ceramics / roller bearings.

I would also very much agree that a 2.5 will have an enormous advantage , and perhaps the best way to get the WRX to 350bhp is to go with a stroker But Iam trying to do it for people without the need
for a costly build , mine is 3500 but its still at 2,03 so its close to what most people have.
.

Linksfahrer

No offence taken

The 2.5 graph really shows what's going on ! At 2100 you are already at 140 ft/lb and by 2500 180 ft/lb, I currently get only 125ft/lb by 2500rpm that is a considerable difference ,
Then yours starts to really fly up with a 70ft/lb gain between 2500-3000 , I make only 25ft/lb in the same rpm area . The 2.5 has 23% more capacity but manages to generate 3 times
the torque increase in that 500 rpm. So something else is going on , and I think its down to the physical amount of gas /gas pressure needed to overcome initial turbo wheel inertia.
The twin scroll routine must really help a lot here,.

But once I have the ported heads back on , and Martyn does the before Dyno run graphs we will know more of the effect on just the header porting .

Following that I hope he can wring a bit more torque out, up in the mid range . (what happened italics was rather less) 150ft/lb 120 at 2500 would be great
getting to 250Ft/lb 150 by 3500 instead of 3850 would be a major step forward , and 360ft/lb 357 4500 , holding 350 ft/lb 310 till 5950rpm fantastic and really time to stop before the 5 spd box goes pop.

Tidgy

Mine was a single scroll not twin scroll. It was a custom billet GT2871R.

This was the initital result after the engine build, Running on the Stock Type R gear box, top mount and standard V5 STI headers, it was also limited to 1.2bar as it would have been too much for the box to take



It then had front mount, GT spec gen 2 headers, syvecs S6 and a hawk UK 6 speed fitted to get the result in the previous post.

One thing you need to consider though is you also need to look at the Boost graph as well, additionaly you will gain some spool on the road vs dyno (but that will be the same in all case so can be ignored for the purposes of this).

The initial result looks great on paper, but suffered a bit in lower gears where the turbo couldn't keep up with what the engine was producing so it was reving faster than the turbo spooled so didnt pull as well in 1st and second, then 3rd it just took off like a rocket. The longer ratios in the hawk 6, which is designed to work with the 2,5, means engine has to work harder so turbo keeps up. (hopefully that makes sense lol)

Linksfahrer

Tidgy ,
The WRX is of course at a flow disadvantage in the lower revs due to lack if STi AVCS , the Sti optimised valve timing gets a lot more gas moving earlier.
However the higher up the rev range the effect of the optimised valve timing lessens a little.

So your 331bhp graph for first build is still impressive you are getting 350Ft/lb at 3300 rpm, before adding the GT spec gen 2 headers (Scooby clinic appx £600 ) FMIC / Syvecs
the most interesting thing here though for me is that on first build you have 150ft/lb at a very low 2300rpm that climbed to 250ft/lb by 3000rpm.
I know adding the later mods / remap made 10ft/lb and 20ft/lb more for the 2300-3000 range, which is small change to what happened later :
the real big gains for your final engine setup came past 3300 with huge gobs of torque till 5300 , had you wished I'm sure 400bhp was on. However I digress

I have added an earlier graph from 2018 showing my car on the last 2.0 engine , it was done on a China TD05 16G at SRR , to be honest I was rather disappointed with that result
especially as Duncan needed to wring its neck at the higher revs even to get to 311bhp ( I think around 1.6 bar if I remember ) .

The area I am currently interested in is again the 2500-3500 band, here you will notice that very little difference can be seen to my latest 328 bhp curve.
That's despite adding Harvey's trick pipe the SC36 turbo the Sti TMIC and 30cc more cubic capacity.


At 2500rpm 125ft/lb is identical 3000rpm 150ft/lb ditto 3500rpm 195ft/lb is 5 higher than latest 3800rpm 250ft/lb identical Only then does my latest combination +

So I can see that even the China made TD05 16G is not a bad deal, at least till the bearings got sloppy anyway.

Now I'm going to throw in a graph from Henrik's old 2.1 (also on a Sc36 )

I find this result devastating its the same tuner RR and turbo and his torque figures for a WRX !

Henriks got 150ft/lb Torque at 2500rpm and 200Ft/lb at 3000rpm a full 500rpm earlier than mine. surely 70cc capacity does not mean that much of an improvement ?
his peak torque is identical at 325ft/lb but still comes in 500 rpm earlier and is held longer.
all I can think of is the low speed exhaust flow / then later better overall engine breathing , of course I don't currently know his final boost level but...
what am I missing ?

Following info ( RCM headers ) posted by Henrik later , the other interesting feature on this 2.1 graph is the peak power flat curve shape.
The ability of the engine to flow freely is demonstrated by a very flat peak achieved near 6500rpm that is held flat till 7300rpm
>97% of peak power is achieved over a full 2000rpm band.

On the standard smaller TD04 sized turbo even a PPP WRX 2.0 @ 265 Bhp peaks asthmatically just below 6000 thru 6400 rpm and dropped of sharply either side.

A wider predictable power band makes the choice lending itself well to use of the higher ratio 5spd box, less gear change sensitive to push on quickly cross country.
Also making a forgiving track car, that band creates a play area which you can use cleanly through an apex, its such a useful feature as you don't upset balance attitude
while you stir around for the next optimum gear.

Tidgy

The heads were v5 sti, so no avcs on the posts i made so that won't account for it.

Could it be a cam difference?

Henrik

iTrader: (5)

So the 2.1 et build wasn't done for me (just a point of order). It was originally built for a guy called Malcolm, but I bought the engine and car off him 🙂

The 350hp graph was with RCM headers as well, which should have made spool slower, assuming our assumptions are correct (are they?)

I'm really looking forward to your Dyno graph, linksfahrer. Great to see more like minded people chasing spool and lag rather than big power

Having said that, Tidgys graphs both look awesome! Sensible hp target whilst still maintaining spool due to the extra 0.5l.

@Tidgy , was this engine also on type-r heads? I wonder what they do for spool etc. Certainly the WRX heads seem worse up top even at high 300s.

Tidgy

Same castings amd cams, but supetech valve kit, valves and springs

Henrik

iTrader: (5)

​​​​​​I must learn to read the full thread

Tidgy

Haha, tbh im not sure if I said heads were reused or not

Linksfahrer

I looked these up , and the claim blurb "For naturally aspirated motors these valves will give you a much greater cylinder flow for good HP gains." is interesting but from the photo I could not see a valve profile shape change
I was expecting a rimflow design , however what was interesting though was the kits double valve springs , I used to use these on mini engines to prevent valve bounce at high rpm ,it used to be an issue on the 1000cc when you got to 8k rpm.
The kit also has nicely engineered valve guides for reliability but I think they are mostly of "high end" benefit.

Tidgy

Its more the strength that the change was done.

Linksfahrer

As far as I can read from multiple posts over the years , all the mappers feel the RCM headers are excellent, My assumption (that's all it is or was ) that they might have a
larger bore than the Std WRX pipe does,

In theory a larger bore give a much higher choke volume ( where resistance to increased gas volume passing starts to be significantly a lower rate of return versus the increased input pressure)
this would also support the much higher bhp that they undoubtedly are capable.

What does not quite add up for me with Henriks 2.1 (*Malcom) engine is that it produces so much more bottom end torque,
Through the mid eighties I put a lot of time learning and following David Vizards bible on tuning Mini's and at least in the normally aspirated world ,
gas speed is really critical for that low rev initial torque. That is underlined by high compression ratio's and chamber flow improvements.

Whilst I can see from that 2.1 Torque curve that it reaches a flat plateau , I cant say if calling for and getting more boost from the SC36 was possible
If so could it have developed still more torque and held it longer across the rpm band. Knowing now that an RCM header was on I certainly don't think
that they would have been the choke point. What it does confirm though is that you do develop a lot of torque with a good design.

This still leaves me now , with some good expectations following the WRX casting porting. I don't believe I can get to Henrik's lower rpm figures ( being 70cc down )
and I might be running a lower CR, but that can be partially compensated in the boost map once the Turbo can provide it.

Just have to wait till Plymouth engine Tune can get them on ( I'm booked for 18th ) and the Dyno figures to follow up.

TECHNOPUG

iTrader: (1)

200lbs/ft by 3k makes for a great road car IMO. Less important for a track car.

I reckon the porting work will start your power band 10% lower down the rev range.

Linksfahrer

Well it turned out to be just 5% earlier but I have put all the graphs into the opening of the thread ,
and hope the conclusions are useful for others looking for proof or what does what.

200lb/ft @3500rpm +30lb/ft at 4000rpm

330lb/ft @ 4500 +10lb/ft 343 bhp @ 6500 rpm up 17bhp at 6500 rpm

Henrik

iTrader: (5)

That is a great update @Linksfahrer , thank you for doing all this expensive work and posting before/after graphs ! I find it very interesting indeed

Very nice to have on paper what ported headers do torque and power-wise!

SmurfyBhoy

Pretty sure the SC36 is a journal bearing, Blouch offer a ball bearing TD05 16g. The XT-R series

An i right in saying the higher power run was done in January vs Lower power one being done in August ?

Temps play a massive part in gains too be great to know that sort of data.

Linksfahrer

You are right that the 328 bhp run was on 7th August 2019

Using www.timeanddate.com/weather/uk/plymouth/historic Ambient temperature was 17 Deg C 1010mb
You can review the updated results in the lead post from me showing a Dyno run pre check before yesterdays mapping.

Actually this shows 326 bhp so actually down a 2bhp in peak compared to August 2019
but it was still showing a bit of improvement in torque. Following remap we developed 343 bhp

Plymouths PM temperature was 10 Deg C Ambient at 1011mb

By how much should we discount the improved figures with an Ambient temperature difference of 7 degrees ?

Maybe < 1% for 3 degrees C , but does the Dyno output not apply a correction for this anyhow ? If Using DIN 700200 they do

SmurfyBhoy

Unsure on how to correct for temps

I see AT & IT on the sheets i can only guess those are Air Temp & Intake Temp ?

AT. 21 & IT. 24 vs AT. 12 & IT. 17

Most dynos will correct to DIN standard tho i'm sure so my point may be moot. Was just a thought.

But my 100-200kmh times in 140i were 7.8-7.9 @ 13 degrees

& 7.6 in 3 degrees

Same stretch of road. Same amount of fuel

I have read that it's between 5-10% per 10degrees celcius

Would love a dyno operator to confirm this or even if its close.

The gains in spool are worth it alone tho.

I prefer to go off accelleration figures due to how easy dynos can give diff reading. Can be strapped down a tiny amount less & increase numbers

Although acceleration figures are easy to manipulate too

Full tank vs half tank, slope changes, temps & DA all affect times.

Linksfahrer

Well your road timings and observations are entirely correct , on a cold day your effective air intake temperature will be greatly reduced by your Intercooler, this enables a higher density charge of O2 to be achieved at any point along the rising boost curve until the ECU sees the boost level called for in the Map , at which point it will open the boost controller solenoid valve. Therefore YES at low temperature your through the gears acceleration times will improve as the amount of O2/fuel mix available to the engine at WOT will be highest at the lowest Intake & Ambient temperature levels.

The Job of a Dynometer is however to show "the corrected actual" power developed in any given set of environmental conditions,
it does this by applying correction factors against a base run, If the correction factors are not applied then you can never compare data from day to day.

The cross check to the Website for daily temperature/environment to the Dyno sheets for AT IT RH and BP at Plymouth engine tuner shows us that the Dyno Dynamics correction factors were being applied on Jan 18th Dyno Dynamics Correction Factors:

• Barometric Pressure = BP
• Relative Humidity = RH
• Ambient Air Temperature = AT
• Inlet Air Temperature = IT

We / I can assume :

• That Martyn has a work routine and 100% work ethic that does not differ as an employee who has no direct gain by manipulating AT sensor positions or CFs, and that he has genuine professional interest to follow the results ( I know he is addicted to finding power on his own car ). There are very many ways in which you could manipulate a reading but I have no doubt that Martyn does his best to let the modification result speak for themselves. I note too that his Dyno records AT is lower than IT and that this delta climbs on the graphs during his testing. ( a TMIC heat soak issue that greatly influences low speed road performance and that can only partially be mitigated by hall cabin blowers.)
• On the day Vehicle strap down was a constant while my car was pre and post modification dyno plotted , and while he had to ask me for the previous German registration number before overlaying and the Aug 2019 data curves from the Hard disk memory, are good factual representations.
• Following the modification the final mapped result was made in situe and it that took place all between 15:14 and 15:39 on same day Mon 18th.

So for purposes of measuring an absolute power gain for just the mapped improvement of a single modification carried out
Its as good as it can get on a Dynamics Dyno with a single operator.

Base assumptions:

• Engines make less power at altitudes than at Sea Level .
• Engines make less power at higher temperature.
• Barometric pressure reduces with altitude Air is denser at SL.
• At same (Sea) level , BP mb and RH % and where AT = IT the engine must make the same power.
• The reference point for these correction factors are set - according to SAE or DIN standards.
• Static correction factors are not seen in any Ply Enginetuners outputs ( i.e. they do record variation in air temp & barometric pressure ,RH )

An engine will not make the same power from one day to another as weather conditions are changing. Without a correction factors dyno readings from day to day are not comparable. Therefore the difference in an ECU tune tested on any given day should be ignored if correction factors are not present.
For an explanation on Dyno correction factors there is some excellent reading available from R Shelquist at http://wahiduddin.net/calc/cf.htm

SmurfyBhoy

Yea plus on the road with proper air flow you will likely make even more power again. A fan in a dyno cell cannot come close to replicating real world @60-70mph

Extra airflow over the IC will result in power increases too. Q

Linksfahrer

I have been racking my head thinking about the sub 3500rpm Torque levels , Why is it so low on my SC36 dyno run against most everyone else's You may remember earlier my perplexed statement "what am I missing ?"

Henriks (MalcomB's) got 150ft/lb Torque at 2500rpm and 200Ft/lb at 3000rpm a full 500rpm earlier than mine. surely 70cc capacity does not mean that much of an improvement ?
his peak torque is identical at 325ft/lb but still comes in 500 rpm earlier and is held longer.
all I can think of is the low speed exhaust flow / then later better overall engine breathing , of course I don't currently know his final boost level but...
what am I missing ?

Well now I know why History The SC36 (replaced my TD05 16G) and new Forged E207 block and 3 Port controller were fitted by a German garage just prior to my return to blighty Jul 2018
being very diligent Germans many new hoses were replaced to make a good installation.

After my first Supermarket shop today following Mondays collection from Plymouth Engine tuner , where Id had also had a new Samco Turbo= IC pipe fitted , I just thought I would spray some Leak finder to see if I had any minor boost leaks
and I did actually find a tiny bubble coming from the 5mm Turbo nipple pipe joint , as this pipe was a new one all I had to do was to whip it off find a small clamp in my box to solve that. Then some Deja vu occurred , the last time I had that part in my hand
was at my 2013 road map session, Simon had me pull over in the layby and he said , I can't seem to get the normal spool from this Turbo. Did you refit the same pipes when you pulled the TD04 off ? Go check please if you have a restrictor pill in.
I hadn't we drove back to his car and he gave me an Sti one from his little spares box, we fitted it and did another run, with an immediate spool improvement.

I looked at my nice new piece of tube Ah ha , no lump = no restrictor inside. In fact what the German garage had done was to leave the old 2 Port Assy in situ and had just tie wrapped all of it into a bundle on the wing under the 2 port Solenoid.
Ten seconds later hey Presto I find my restrictor pill still in the original pipe.

Here are some photos explaining where this little brass "Pill" with its very fine bore hole is fitted



Excited I thought oooh what luck and promptly stuffed it into my new pipe and back onto the Turbo nipple. Test Drive , Immediate better response low rpm Super , lets open her up , Whoosh ... Loud BOOST Gauge alarm set 1.6 Bar
Of course the new map developed using Port Boost controller was not expecting that , But as I have a map switch , I flopped that over and used the Lower 1.2bar limit no problem , still very good low rpm response ,drove home.

Luckily I for me I had fired questions into Simon and he had explained to me the need to use Restrictor Pills of different sized internal diameters for different engines / turbo combinations in order to get pressure up in a controlled manner.
Until the wastegate spring actuator ( cracks open typically 0.5bar / circa 7psi ) The Pill he had given me was a smaller diameter Sti one to tickle some more boost at low rpm. Therefore I knew that if I wanted to reduce the effect / and prevent an over boost
then Id just need a larger diameter one before I could safely switch back to my 1,45 bar Map. Off I went to find my engineers HSS drill set.

Here are the choices for our different cars with part numbers





If Id had this I would have used it.


After test drives finding that 1mm and 1.1mm still gave an over boost alarm (now set at 1.5 bar)
I think 1.2mm would have worked ok as on the third run out I did not breach a lower 1.5bar limit set point on the Gauges audible alarm .
But to be 100% sure I eventually drilled to 1.25mm ( 0.0492 ) and that has proved to work fine.

Clearly I had been running at low rpms a much reduced less than ideal level of boost, however once a set bar level in the Map is reached the ECU will operate to closed loop control on the 3 Port to ensure the right AFR is maintained.
and what I will now have to do is run another Map/Dyno curve to check and post again the torque improvement found.

Now I don't expect any gains above the maximum 330lb/ft @4500 currently achieved, but I might now finally see 200lb/ft @ 3250 and 250lb/ft @3500 so pretty much everywhere on the way up just 250rpm earlier.

Although annoying that the missing pill was negatively influencing the Spool up, the findings in my investigation are all still Transparent ,
as the comparisons were all made from the same playing field.

I'm happier now, won't need now to pull the head gaskets off in the attempt to raise CR . not yet a while anyhow

Linksfahrer

After having made this post , I have had two knowledgeable people chip in the PM and a Tel call , informing me very kindly that putting the restrictor pill into the tube between the Pierburg 3 port and the Turbo nipple really should not make any difference at all
/ other than potentially causing an overboost ( which of course it did , until I bored it out ) . Although I was given the benefit of the doubt that you might see a dynamic difference whilst road driving compared to a WOT pull on a Dyno , here relating to the instantaneous
feel you get as you put your foot on the throttle.

However the only way to deal with my I think my Popo meter is telling me is to get the car back on the rollers, Id ask everyone reading the "Pill" post to give me and the Vaccine some time,
and if I am wrong I will have to "swallow the pill".

In the mean time if anyone comes up with an idea on how to close the Sub 3500 rpm Torque gap seen on my SC36 versus the target which is Henrik/Malcbs 2.1 graph
then please do keep the suggestions coming.