Fellas,

This is one for the real engine diehard's I quess.

My engine,is an Jap.imported WRX one,which produced std.260BHP in Japan on 100+fuel.This engine has hydrolic lifters,and different camshaft's/cilinderheads,and smaller injectors compeared with my original blown up MY'99GTT-engine(MAF-failure)
The engine kept it's original smaller injector's(380cc?)because my MY99-ones didn't fit.All the other original stuff is mounted on the 'new'engine,and therefore it runs with my orig.MY99 ECU.

After ECUTek remap(1.22Bar flat),it produces 280 BHP aprox.This was the figure that rolled out of the DeltaDash Dynorun,in third gear.

The car is really quicker of course on all the usual performance-test's,but now the mystery:
Befóre the remap it topped 255km/hour(170 miles/hour?)and a bit on the highway in German.(One good reason to visit my neighbours sometimes:-))
After the remap,so with aprox.60 BHP extra,it ends up around 240km/hour???(160miles/hour?)

The funny thing is,all motorparameters look perfectly in order, and I mean everything you can think of.My smaller injectors run 97% at 6500rpm,but this still is enough one would say,cause still not the absolute max.I allready placed a Walbro fuelpump,and I am gonna get a fuelpressure-regulator,which should bring the 97%dutycycle of the injectors a bit down,by lifting the std.pressure.

I hope this will do the trick,but I still can't explain why I do not have powerproblems in all other gears.

Is it possible the injectors are having just enough capicity to ensure my engine gets the right amount of fuel in the first 4 gears,but when things are getting really tough towards topspeed(6000rpm+,and very strong frontal windforce)they can't coop anymore?I mean on the edge of their capicity,they fail only when the engine has it's haviest job,to reach topspeed?One LED of my AFR-meter is flickering a bit above 6000rpm in 6th gear,but turbopressure is normal,as in all other gears from 0 to 6500+rpm.MAF sensor is also in good condition.

Anyway,my feeling says I have to look in the direction of the injector-capicity,and therefore will try higher fuelpressure,but I do not understand everything works perfectly well in the other gears.I mean in theory it shouldn't be a problem.

Anyone recognises this typical problem?
All suggestions/advises/technical explaination are welcome!


Grtz.Arend.
Holland

[Edited by DutchClutch - 10/2/2003 9:40:19 PM]

[Edited by DutchClutch - 10/2/2003 9:42:02 PM]

 

John,

My ECU is ECUTekked,and speedlimitation is only due to regulated turbopressure-buildoff.Before my car was ECUTekked,turbopressure(0.85bar aprox.) decreased in steps,starting above 5000rev's? and ended at 0.5 bar(max.wastegate-pressure)
After the ECUTek remap,these steps are also taken,but on a higher boostlevel.
And this is what I don't understand.

Could it be that in 1,2,3 and 4th gear my mixture is already a bit hard to maintain for my smaller injectors,and there is just enough fuel injected?One could imagine,that this could be detected then on topspeed,where the engine has its haviest job.I mean a bit on the lean side is not so easy to feel when running in lower gears.A slightly powerfailure/lean mixture shows up at first under heavy circumstances,or is this wrong thinking?

However,I am not so much interessted in these high speeds,but it should do the job,when one would want to.This car is not made for these speeds I catch your drift on that one.

Grtz.Arend.



[Edited by DutchClutch - 10/3/2003 2:26:24 PM]

 

If the new engine produces higher power at a given RPM then the top speed should be higher assuming the speed limiter is disabled. However, your original MY99 ECU would have had a speed limiter.

I don't think you have an injector problem if your engine is genuinely producing more power than before. If you say it produces less power than before AND lower top speed (assuming delimited) then start looking for faults.

On another issue, even with no detonation and good AFR you can lose a Scooby engine to big end bearing failure at high speed. Who knows what the reason is, perhaps the bearings do not oil well or overheat at sustained high RPM (the only circumstances you do this is a top speed run) and pick up, but autobahn storming a Scooby engine is a recipe for failure IMHO. Jap engines of course have a 112 mph speed limiter, and I gather big end failure is very uncommon in Japan.

 

It may be something to do with how your intercooler is operating at that speed.

I've seen on here threads that indicate that it does not work very well at +100mph, maybe youre getting det at the higher speed and the ECU is retarding the ignition.

The standard ECU map AKAIK is very rich so maybe not no much retard.

Just a theory.

Rich

 

Maybe it just so happens that your 255kph is at your peak power rpm, but after the remap peak power is earlier but power at the RPM for 255kph is now lower?

Just a bizarre thought

 

I would suggest you are not really doing 170mph with 260bhp ?? Speedometers are notoriously inaccurate, usually reading more that 10% above actual speed.

Looking at speeds from the totb trap speeds it would appear that an Impreza needs well over 400bhp to do a genuine 170mph

Cars with around 350 bhp were struggling to even reach 160mph

Andy

 

Andy,

My topspeedfigures are of course not the real ones,and indeed the speedometer-figures.But the difference stays.

Topspeed keeps a mistery to me,but the most important thing is,the car is realy faster on all acceleration-test's,and runs very smooth.

Maybe next week with higher fuelpressure,things change the right direction.I also considder to buy a brandnew MAF-sensor,just to be absolutely sure on that one.
I will let you know by then.

Grtz.Arend
Holland.

 

It does not help your problem but 255kph = 159mph. On Standard gearing both my cars speedos were out by 8-10% at speeds over 100 mph (160kph) KPH to MPH x .625 or divide by 8 and multiply by 5.
MPH to KPH x 1.6 or divide by 5 and multiply by 8.

Has anything else changed at the same time? Air filter or induction system. Did you check the speed on the same bit of road and were the wind conditions the same???

 

Harvey,

The 255km/h I reached on a flat road,with (allmost)no wind.This was in the morning when we where traveling haeding the WRC in Germany last year.The road was pretty deserted at that early hour,so a perfect time to try topspeed with my then 'new' jap.WRX-engine.

I tried several times now with aprox.60BHP+,but even with the wind behind me back,still max.240km/h.

One (important?)thing I did not yet mention is that I have a downpipe with a 'closed' flens behind the wastegate.(So not a bellmouth-type)The pipe comes from a rallycar from Poland,and is also slightly smaller in diameter when compeared to the std.2,5inch.
Maybe a 2.5"ScoobySport bellmouth DP,will improve things,because of the higher turboflow due to ECUTek remap.The one I have now may be a bit too restrictive on high RPM's.It's just an idea.


Arend.

 

An open neck down pipe will not hurt and could provide a noticable improvement. Contact Hayward and Scott who were the original manufacturers of the SS D/P. They do a 2.5", a 3" which tapers to 2.5" and a full 3". I use the full 3" and am happy with it. Depending what you intend in the future you may wish to consider the 3" to 2.5" if that is the diameter of the rest of your exhaust system.

 

In that case I would go for the 3inch that tapers to 2,5.This in theory would give the best flow I guess.
I do not want to go further than the 280BHp I have now,so the 2.5inch for the mid(std.with cat.),and end(ScoobySport)I have now, should be enough.

I know that 'bellmouth'-types are made for improvement in the higher rev's,but do they also improve topspeed in practice?


Arend.

 

If you have the data from a rolling road, try checking the respective torque curves. Different engines have different torque characteristics. Maybe at the top end the old engine had higher torque than the new engine ?

 

3" to 2.5" may give better spool and top end.

 

Thanx Harvey,time will tell!

Britt,

We are talkning about the same engine,befóre,and áfter remap.(+60BHP).Torque is also higher on any given moment,but topspeed lower,that's the 'funny' thing.

Grtz.Arend.