Power Loss At 5000 Rpm With Efi ?

[Saveit 0]

Hi Guys,

 

We have a 205 1,6 GTI 8v bottom with a Longmans top, Jenvey TB's and EFI EURO 1 engine management.

 

We were finetuning it on a RR, which resulted in complete power loss at 5000 rpm - have any of you tried this ?

The engine runs perfect and smooth and everything looks fine up until 5000 rpm, but from then it completely looses its power, meaning it maxes at 5000 rpm with only 110 bhp or so ?!

 

Any bright ideas ? We are completely lossed here as everything looks and sounds fine !

 

Thanks

[James_R 3]

The ECU isn't loosing the crank signal??

[welshpug 1,670]

should be able to see what's happening on the laptop from the data

[Saveit 0]

We have tried putting an EFI crank sensor on since the EFI-guy said it might be loosing crank signal. Now it just flattens at about 5000 rpm until 7000 where is has a slight peak resulting in 121 bhp

 

The EFI-guy believes it is due to the CR being too low for the camshaft. The Longmans top is from xsportracing and is the best you can get for an 8v. It made 225 bhp on a 1.9 high compression engine (specs can be seen on xsportracing.com). So although ours is a 1.6 it should definitly put out more than 120 bhp.

 

The inlet is Jenvey 45mm with DCOE style port matched manifold and 4 inch air horns.

 

Now the camshaft is a piper cam "hot rod" thingy at 328*. Camshaft have been adjusted to the 5.71 mm lift @ TDC that piper cams describes. Now, the EFI-guy believes that the CR is too low. The engine has standard CR of 9.8:1. I would imagine that the head have been skimmed a few times before, and i had it skimmed myself. So would imagine the CR would be at leat 10.5:1. I know this isnt really that much, but the engine is for endurance racing and therefore we have tried to keep the CR at a reasonable level so that the standard pistons can cope over time. Could this be the reason for it not putting out more than 120 bhp and 7000 rpm now?

 

According to the xsportracing it should be around 170-180 bhp or something close. It definitly isnt.

Edited August 24, 2009 by Saveit

[welshpug 1,670]

have you checked the cam timing? has it ever revved cleanly to 7k?

[Saveit 0]

It revvs fine and smoothly. Sounds perfect. And yes, cam timing have been done with precision and the lift is just about perfect at TDC.

[brumster 135 1 Cars]

I run EFI myself, but on an mi16. Can't think of any EFI-related reason as to why it would be so. Are you running/mapping it with a wide band lambda and self-learn, or doing it the old fashioned way?

[Saveit 0]

I run EFI myself, but on an mi16. Can't think of any EFI-related reason as to why it would be so. Are you running/mapping it with a wide band lambda and self-learn, or doing it the old fashioned way?

 

The EFI guy is using a wide band lambda and self-learn and he cant find out whats going on.

I cant see any mechanical reason as to why the curve flattens at 5000 rpm - must be electronic - meaning somewhere in the engine management setup.

[James_R 3]

Compression is going to be massively low on that cam, it wants more like 12.5:1 compression on it, but that would cause the bottom end to be screwed up. As said above recheck the cam timing, could be a weird pulse mismatch cauing it, have you tried removing the airhorns and check if it makes any difference?

[Saveit 0]

Compression is going to be massively low on that cam, it wants more like 12.5:1 compression on it, but that would cause the bottom end to be screwed up. As said above recheck the cam timing, could be a weird pulse mismatch cauing it, have you tried removing the airhorns and check if it makes any difference?

 

Ok, so you are saying we should either increase the compression massively to get the appropriate setup for that cam, but then we risk blowing the bottom, or maybe better changing to something like a 289 degree cam ?

Cam timing has been readjusted.

[Tom Fenton 1,554]

Check for standoff, you may find you need a longer inlet tract. I've only ever seen this once, and not on a Peugeot engine, but with a long duration cam as you are using.

[Saveit 0]

Well we managed to pull out 170 bhp @ 8000 rpm by calibrating the dyno and messing with the ignition tables. Think that is very good for a 1600 8v. If we installed some high comp pistons for a CR of about 12.5:1 then we would probably hit the 180 bhp mark.

[James_R 3]

so the advance wasn't high enough on the map??

Edited August 25, 2009 by James_R

[Saveit 0]

Yes i believe so. Didnt really understand where the big change was. But the mapper said that they had messed around with the ignition map for a few hours and the bhp grew steadily. After then resetting and calibrating the dyno it all came together.

[James_R 3]

Good result, can you post up the dyno graph??

[Saveit 0]

I sure can. The graph is quite uneven which should be due to the CR being to low for the 328* cam according to the mapper. I am not convinced though. I believe he could finetune a few bits and bobs in the fuel and ignition tables to sort it our.

 

Will post it when i get home tonight.

Edited August 25, 2009 by Saveit

[Saveit 0]

So heres the dyno.

 

I think ill be changing the cam to a cam better suited for a 1600. Piper has one that should be the best for 1600 engine and that is 308*. This cam is made for 1900 engine and therefore is a bit too aggressive. Will be trying to sell it at some point. Furthermore we will be upping the CR to around 12:1. These two things together with some more fiddleing with the ignition and fuel tables should hopefully produce 180bhp+ ... Would like to hear you guys opinions in this?

 

Edited August 25, 2009 by Saveit

[James_R 3]

can't see it

[DrSarty 92 1 Cars]

can't see it

 

I've e-mailed it to you JR.

[James_R 3]

Thank yoyu my dear

 

Looks good, torque is rather flat though and torque/revs cross a bit low down to the rev's looks low if anything, still nice result to get you started, which I have that end now

 

70lbs/Litre is pretty good too!!

Edited August 26, 2009 by James_R

[Saveit 0]

Yes we have some to improve, but we are rather close to the goal which was 180bhp. And we would like to smooth the curves a bit and avoid the dips. But with a milder camshaft made for a 1600, higher compression, and finetuning of the fuel and ignition we should hopefully reach 180bhp and a more smooth power curve.

[James_R 3]

I'd be interested to know your Hydrocarbon's CO at idle/1000rpm

 

I had issues with my engine emissions at 900rpm it was making CO 1.2% and HC 4500!! my guess was the overlap pumping the air/fuel out the exhasut at those revs (282deg 12mm cam 10.5:1 CR)

[Saveit 0]

Huh...

 

Well if its the lambda mixture you are talking about its right at 1 (14.7:1) when idleing. EFI uses some selflearning system where you just hook up a widebandlambda and it will map itself close to perfect. But my mapper also edits the tables to avoid using many hours of driving with the self learning system on. But at idle the car has mapped itself.

 

What is your engine specs and what management are you using. Would love to know your results if yours is a 1600 also?

[James_R 3]

I've not got any RR results for mine yet, will get it on an RR in sept sometime hopefully though, spec's roughly are

 

1760cc

10.5:1

282deg 12mm lift cam

1900 management

1600dizzy

BCR8ES plugs

 

that's the powermaking end of the spec anyways. I want to put better valve springs in to rev it more as I can only go to 7000rpm at the moment and it's still making power up there, but not been able to get hold of puma racing for his single springs (doubles are too expensive for me) the cam is advanced more than the manf recommendations as it's for a 1900 engine and I wanted to bring the power down. Also I have a "ported" head to go in with different inlet, I'm trying to keep it all as cheap as reliable as possible.

[Saveit 0]

Looks good. Mines in a bit higher price range though. Its a fully ported longmans top, double valve springs, hydraulic lifters, 328* piper cam, 45mm jenveys, EFI management, BCPR7EY and some other things that i have forgot