ric

Hello!

Can somebody give me an answer on the following topic:

Which setup does give more power/torque:

Standard TD04 turbocharger running at 1.2bar boost from 3000 to 5000rpm then dropping down to 1bar at redline.

IHI VF23 turbocharger running at 1.2bar boost from 3000 to 5000rpm then dropping down to 1bar at the redline.

???

..or does a bigger turbocharger give more power at the same boost levels?

greetings
ric

Sam Elassar

hi ric
i think i can answer this one from my own experience.
car is my99, link , ehxuast.
TD04L TURBO 248bhp/ 269lb/ft runing 1.2 bar
VF23 TURBO 278BHP/ 285 IB/FT running 1.2 bar

all done at the same rolleres ( star perfomance) for comparison standrad cars gave 200-210bhp, stis gave 260bhp and chipped cars around 250-260 bhp on these days.

so bigger turbo will flow more air at the same boost level which means more power.

the VF23 is the best mod i have had done after the link. you get more lag but it means you drive one gear lower to get it back but the difference at the top end is HUGE

top cat
more boost = more power so if you turn you boost down you will get less power and torque and if the boys with the hybrids increase their boost they will get a hell of a lot more

Sigmund

Boost is boost no matter what turbo produces it.
But: A bigger turbo will take longer time to get the turbo boost up where you want it (known as lag), and it will be able to produce higher boost at higher RPM as they can move more air.

Smaller turbo will give quicker response (less lag) and it will not be able to hold high boost so far up the rev-range as a bigger turbo.

Soren

Ric,

Sigmund is mostly correct.

However, at the same boost level, a turbo with a larger compressor is more efficient at moving air. Better efficiency equals lower air temperature,lower air temperature means a denser charge. A denser charge can result in more HP since you can add fuel.

For example, turbo A requires 125,000 RPM for the compressor to produce 10PSI. If turbo B requires 100,000 RPM to produce the 10PSI, it will be a "cooler" 10PSI and thus more dense. More dense means more O2, more O2 means you can run more fuel.

Does this make sense?

Soren

BugEyed

Looks like you've already got your answers, but I can't help but add my two pennies worth.

The objective of the turbo is to push as much air (and hence oxygen) through the engine as possible. Hence, the comment that it is not just the boost but also the charge density that counts. This is why the intercooler and its design are important as well as the turbo.

Does size matter? Well in the turbo department it does. The trick for the engineer is to use as small a turbo as possible (and hence keep down lag) to get the amount of air required into the engine without the turbo running into choke (which is where it cannot pass the inlet air through the compressor or the exhaust through the turbine, and hence effectively stalls).

The Escort Cossie could be had with a big turbo (to homologate it for rallying) which on the road version gave no more power but lots more lag. However, the small turbo was no use for rallying as at around 300 horsepower (and the works boys have a lot more than this limit) it ran into choke.

My question to the more knowledgable is, what is the limit for the Scoobies standard turbo?

R19KET

There were two UK spec' cars at the PE RR day last Saturday, running hybrid turbo's.

Danny's car had full exhaust, induction kit, Link ecu, and hybrid turbo running 16psi (1.1bar), it made 289bhp/260ftlbs !!!

Pat's car, full exhaust, induction kit, Pectel ecu, water inj', BIG hybrid turbo running 16psi, it made 307bhp/263ftlbs !!!.

Mark.

TopCat

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:<HR>Originally posted by R19KET:
<B>There were two UK spec' cars at the PE RR day last Saturday, running hybrid turbo's.

Danny's car had full exhaust, induction kit, Link ecu, and hybrid turbo running 16psi (1.1bar), it made 289bhp/260ftlbs !!!

Pat's car, full exhaust, induction kit, Pectel ecu, water inj', BIG hybrid turbo running 16psi, it made 307bhp/263ftlbs !!!.

Mark.

[/quote]

My Car was also at PE that day MY97 UK

275bhp/277ft lbs!!! SS full system K&N filter, Superchip running 20 psi , could get more torque if boost was turned down.

Not bad for a UK car hey??!!

TC

AndrewC

This may seem a stupid question but:

What exactly is a hybrid turbo?

Andrew...

YorkshireSimon

Can I throw in another question.

What is the difference between VF22, 23 and 24? Always wondered!

If I was to put a Link ECU on my MY00, which would be the best VF to go with. Also, keen to see what this hybrid is all about (previous question)

Cheers

YS

Sam Elassar

vf22, and vf23 are identical externally but the vf22 have a bigger compressor. ie more power at the same boost level but also more lag, not very suitable for a UK cars which you should only rev to 6500rpm. so a VF23 will be more suitable decause the power will come quicker however saying that most Australian tuners recommend the VF22 ? i suppose it will be better for track days. VF23 is what you find in most 22Bs

VF24 and 28 are very similar i think the vf28 has got a smaller compressor ( i know pete cronoy had one in his race car) . both again they will be good on a UK car, the VF28 is what you find on sti5,6 and the P1.

hybrid is when you give your turbo to a tuning company like turbo dynamics et al and they replace the internals to your requirements and car specs. ie flow more air, spool up quicker to increase response this sort of thing. usually you can come pretty close to getting best of both worlds

[This message has been edited by Sam Elassar (edited 19 April 2001).]

R19KET

TC,

Like Sam said, if you turn your boost down, you will reduce both your torque, and your bhp figures.

Your figures are great, but you are running 20 psi.

I remember Mervyn at PE saying that you would expect to get roughly 7 bhp, and 10 ftlbs for every 1 psi increase, if this were accurate, that would give Danny 317bhp, and 300 ftlbs, if he were to run 20 psi......not bad for a UK car

Mark.

YorkshireSimon

Nice one Sam, been bugging me for a while now that one. Having had my MY00 for a year now, I am starting to get the uprate bug and the turbo is one of the things on the list, although I think I will have to make engine internals bullet proof first.

Cheers

Simon

NDT

nobody mentioned back pressure.....

the more efficient (bigger) turbo should lead to a lower increase in exhaust back pressure for a given intake boost (or give work done on the intake charge) - so will give more power and torque for the same boost and intake air temperature.

Jake

But can a UK cars internals safely deal with a VF23 producing 1.2 bar boost????

ric

Thank you all for the very informative answers.

It seems that with a bigger turbocharger you can get around +30bhp.

The BIG question is: "Is the UK-engine able to bear these big turbos running at 1.2 bar of boost?".
Here in Switzerland there are a lot of Scoobies that are running with 1.25bar of boost (on the TD04 OEM charger) without any problems. It seems that the internals can withstand this boost level.....but I am not sure at high rpm?

Sam:
You had both on your car: Is it really that much faster with the VF23???
I am not sure but if you write youre running the turbo at 1.2 bar you mean the peak boost. I think you now use the VF23 with higher boost levels at higher rpms than the TD04 was able to produce?
....so what are your boost curves?

greetings
ric from Switzerland


......thinking about VF23 with Unichip.......

Sam Elassar

NDT
hi due to the reduced back pressure does that mean theoratically you should use a bigger diameter exhaust system with the bigger turbo ?

ric
"Is it really that much faster with the VF23???"
yes
the boost peaks to 1.3-1.32 bar and it holds 1.26 bar all the way to 6500 rpm after that i tail the boost down to 1 bar. the car has been running like that since sept-oct last year and it has done around 6-7 track days at least.

the curve is flatter with the bigger turbo which is what you should expect as the TD04L is not really designed to operate at this level so it is over spinning to acvhieve 1.25 bar producing at lot of heat. the VF23 is very comfortable at this level.

there is a lot of cars running even bigger turbos with no problems, you just need to be careful with your mapping. and keep an eye on the knocks.

EvilBevel

Hey guys,

I can confirm what Sam says: I'm running a VF23 / Unichip combo. With my previous setup (1.2 bar boost with TD04L) I got about 255 BHP, whereas with the same boost the VF23 produces about 275 BHP on that same RR. Torque went up about 15-20 lb/ft at 4000 rpm

Since then, the car was mapped very much like Sam going from the description: 1.33 bar from about 3000 rpm (a bit later than with the TD04L, there are no wonders), holding that to about 5000 rpm, then going down to about 1.23 bar until 6000 rpm, then taper off to 1 bar.

Map is pretty rich (at WOT, min CO level is 7, but 9 most of the time, *especially* at higher revs.

Ignition was only advanced slightly in the less critical areas for better pickup, but beyond that running on the "standard" ECU settings.

Can't reveal all because of a big shoot-out article to appear soon in the Dutch club mag, but it does indeed go very fast...

Ric, seeing you're from Switserland. Have you ever considered the DigitPower setup ? Very expensive, and very high boost pressures are used BTW.

Anyway, don't think that upping power is just a matter of "safe/not safe"... you will get more wear producing higher power. But with a good turbo and a conservative map, you can stay away as far as possible from the "bang" moment, no doubt about it.

Whatever you do, get a LambdaLink & KnockLink (or similar product), so you can monitor what exactly is going on. Your car may still fail - those LED's are not protecting your engine... but give you the chance to see when things don't look right and back off. I only had the KnockLink register a knock once in 5 months time, and that was when releasing the throttle (lift-off det). It has been set at maximum sensitivity, with a separate sensor. Oil temp was about 93 degrees after 4 laps on the Ring, but I did remove my undertray and use Castrol RS 10W60.

I just ordered an inlet temp gauge BTW, so I can see how inefficient the intercooler will get in summer. In winter, there were no problems. Have ordered an EGT gauge as well, so dashboard is becoming a bit crowded

Anyway, I'm just rambling on: make sure you find a decent mapper is what I really wanted to say ... you can kill an engine in a blink if you don't know what you/they are doing.

And as for the original question: both torque and BHP are directly related to boost pressure (ignoring a few other things here). Boost level between 3000 & 4000 rpm will determine for a large part your peak torque number, whereas the final BHP will depend on how frisky you feel with the boost level at 5900 to 6400 rpm (still talking UK car).

I think

HTH,

Theo

scoobynutta555

I was thinking of chipping my previous wrx but was told, esp. from power engineering, that it was not worth it. As the engine is an alloy block it cannot take the extra power without the pistons going awol, the 3rd piston is most likely to melt!
While i was in their office waiting for car to b serviced they had call after call from owners with chipped cars with the engine blown. So although chipping the car may give u a short time of increased power its really a deal with the devil. U will find the engine will go without serious mods to it, and i mean serious!
The road i went down was to change the car for a beefier model, a sti5 coupe. These cars are specifically built for 280-300 bhp and increase torque etc, and have a fully modified engine compared to std uk specs.
I chipped a car before and ended up on hard shoulder of M1 on boxing day morning after engine blew and turbo got ripped to shreds, £4,000 damage all in all.Enough for me to p/x for a car built to have that power in the first place.

Sam Elassar

scoobynutta
don't you think you are missing the point a little bit here ?!! i don't see in any of the threads the mention of the word chipping !

subaru the ecu is not desgined to cope with more than 1.1-1.2 bar so basically you don't have the appropraite fuel or the ignition advance to deal with that level of boost . also which is even worse the superchip for the scoobies ( i don't know about other cars ) just fools the ecu to think the ecu is running 16psi when it is infact running 19-20 so you end up having an engine that is designed to run 14psi running 20psi with out enough fuel and too much advance with a small turbo running like mad and producing too much heat for that ill designed TMIC to deal with. and BANG. imho off course.

the after market ecus such link and unichip actually deal with the advance and fuel to suit the boost level hence it should be safer.

BTW i have seen and sti 4 type R totally standard with the con rods flying out of the alloy block. according to the owner he was pulling hard in 3rd at 7000rpm at the time. these things could really happen to anybody and any car. although the sti's have definitely got stronger internals they are mapped for 100Ron octan so they are slightly dodgy on UK fuel.

psyg

Hi

I had fixed a IHI VF23 turbo on my MY99 “standard UK”;
it had an open exhaust and a K&N panel-filter;
and the car is/was chip-tuned by EMS (a dutch tuner-mapper; same as Theo above); boost was max 1.2 - 1.25 bar, in optimal weather circumstances sometimes 1.3 bar peak.
After fixing the VF23 a bit re-tuning kept the turbo-boost at exact the same values: 1.2 – 1.3 bar maximum.

After the mod, as Sam said, the car had a bit more turbo-gap, but feels quicker specially at high rev’s.

I liked this mod immediately; but wanted also some more objective feedback than just the “good feel”.
So I did some speed-‘clocking’.
First with the standard TD04L turbo, than next day with the VF23 after 100-150 miles running-in.
It was on the same road, timing in both directions. The second day a bit less weather-circumstances and a bit more weight (plm 20 kg gas) in the car.
Timing: went up till given speed, steady and than full-throttle while starting the stopwatch.
Timing each speed-range 4 or 5 times to get ‘mean’ figures.

Results:

speed* ... gear ... RPM ... time with st-turbo ... time witt VF23

80 - 120 (3): ... 3500-5400 ... 3.4 - 3.6; ..... 3.1 - 3.4 sec
80 - 120 (4): ... 2500-3800 ... 4.9 - 5.3; ..... 5.1 - 5.4

80 - 180 (4): ... 2500-5800 ... 11.9 - 12.2; ..... 11.9 - 12.4
80 - 180 (5): ... 1900-4300 ... 17.9 - 18.3; ..... 20.5 - 20.7

120 - 180 (4): ... 3800-5800 ... 7.1 - 7.5; ..... 6.7 - 7.0
120 - 180 (5): ... 2900-4300 ... 10.0 - 10.3; ..... 9.9 - 10.6

100 - 160 (4): ... 3150-5200 ... 6.9 - 7.3; ..... 6.9 - 7.3

100 - 200 (4): ... 3150-6400 ... 12.6 - 13.2; ..... 12.5 - 12.7

120 - 200 (4): ... 3800-6400 ... 10.1 - 10.6; ..... 9.6 - 9.7


* speed as speedo says; thus not real speed (= not important for comparing, same distortion).

Some conclusions:
· till plm 3000 rpm st-turbo is quicker, between 3000 and 4000 about the same, and above 4000 rpm VF23 is really more powerful.
· Although the difference the in figures is not shocking, half a second between 120 and 200 km/h is 20-30 meters alongside another car.
· I liked to have some more comparing in really high rev’s; pity, didn’t do it the first day. Specially speeds above 200 km/h are different now, and topspeed is higher.
· With VF23 the car can keep up boost (much) better in high rev’s, above 5500-6000 rpm, bit more than 1,0 bar till 6500 rpm and up.
· When you drive the car always above 3500 rpm you have a really quicker car; I did this with other EMS-tuned scoobs, mine is faster now than the others, before about the same.


But it’s clear that such nice big turbo deserves better chip-tuning/mapping, specially in low revs. Such mapping (with Link, Motec or Unichip) can make the car much better picking-up.

Theo-Evil (see above) did it, EMS did it with Uni-chip, and his car now is really a monster!!
I’m one of the following for Unichip, and of course a good mapper, and the things Theo said.

Geert


[This message has been edited by psyg (edited 21 April 2001).]
PS How to make a nice tabel in this BBS?

[This message has been edited by psyg (edited 21 April 2001).]

[This message has been edited by psyg (edited 21 April 2001).]

Danny Fisher

TopCat/Mark, I don't want my car going BANG!!!!

Dan

R19KET

Danny,

That's why you're only running 16psi !! But I'm sure it could be re-mapped to blow up with the best of them If you let ME loose on it

Mark.

Gastro

Sort of related, but since there is considerable knowledge flying around with regard to Turbos.......What is 'overboost', can you detect it just driving normally and if so what are the tell tale signs etc, can it be fixed etc ??

Thanks

Gastro

EvilBevel

Gastro,

Goin out on a limp here - 2 years ago, my biggest knowledge about engines was how to start the lawn-mower

The term "overboost" on this bbs is used for two fenomena:

1) having a bit more boost around 3.200 -3.500 rpm before settling at a slightly lower level (ex: overboosting to 1.2 bar before settling at 1.15 bar. May also be referred to as "scramble boost".

2) the dreaded "fuel cut/face to windscreen" thing, where the ECU detects too much boost, and decides to cut off all fuel, resulting in a) less boost and b) driver going "what the hey ?!"

Still not clear where the n°2 limit lies, but on a standard ECU (or a PPP) between 1.15 and 1.2 bar depending on MY and time spend on that boost level. With other ECU's, that fuel cut limit might or might not be there anymore (which can be a pretty bad thing...)

HTH,

Theo

ric

Today I drove a MY96 (big turbocharger TD05), that runs 1.25bar boost. The curious thing is, that my car subjectively feels faster than this car that produced around 300bhp on the rollers. (My car just has exhaust + cold air duct).
Ok, in the high revs this car pulled like a pitbull, but in the lower revs........not really that convincing.
The owner of this car then drove my car (MY98) and he said that my car was more fun to drive than his. Maybe this is also because the MY96 runs less compression?

I think that objectively my car is slower but round bends I come out of them a LOT faster...

How much is the difference in turbo lag from TD04 from VF23 .... and does the VF23 really respond very fast to your throttle position......maybe I should go the VF28 route...

Evil Bevel:
When this tuning article is out, could you please send me a copy.......or is it in Dutch....I just speak Englisch and German.....?
Digit Power does two things. Stage 1 is a bleed valve and a fuel cut defender (800£ !!!). Stage 2 is a TD05 turbocharger and I am not sure what they do to the ECU.......but it reaches 300bhp but runs 1.5bar peak dropping to 1.2bar held to the redline. Costs around 2000£ (just turbo and ECU, exhaust is also needed). I once testdrove this car.....and believe me, it was bloody fast.....but a LOT of turbo lag, not really what you want on the road. Oh, I personally prefer Sportec to Digit Power.

What is a "conservative map" for you? (boost....?).

I also use Castrol RS 10W-60.

Personally I think that the OEM intercooler is very efficient. Bigger intercooler means more lag........ I have a waterspray kit.......not expensive and worth a try (temp. drops 5°C).

Geert:
Thank you very much for the information! It seems that the VF23 is really faster, but seems to spool up later. If you have a mapped Unichip, please send me the new results.......very interesting to see what a good map can do.......

AS A CONCLUSION FOR ME: Maybe I should go the VF28 route and run 1.2bar to 6500...... I don't want to have more turbolag.

greetings and thank you all for the information!
ric (richimu@datacomm.ch)

Mo

So how would a hybrid TD04 (with larger impeller) compare with a standard TD05?

ric

Good idea Mo!

why not turn a TD04 to hybrid spec???

greetings
ric

Jan Shim

Folks,

In Brunei, the Subaru dealer are supportive of fitting aftermarket parts and we have had many experience with various makes of turbos from VF series to Garretts to Turbonetics for extreme applications including anti-lag.

psyg

Jan,

450 ps???
such a 'monster'-turbo and a UK-standard engine?

Must be fun,
for 1 week, meaby 10 days?

Geert


[This message has been edited by psyg (edited 25 April 2001).]