Engine Holding back

[neal1980]

Having an issue with Rover v8 Twin Turbo (2x td04l) from Subaru running MS2 with coil packs. Also Running a big front mount intercooler. Ive been running the engine in and its been mapped. Went to go over 4000rpm today and its holding back feels really flat.

Flys up to almost 3800rpm then kinda just dont want to rev very well and you can feel the car struggle to produce any more power.

Any idears at all im struggling where to start on this one.

Is it possible only one turbo is producing boost even though both banks are fed too a turbo each side?? Im getting no smoke at all and the boost gauge is reading 5psi.

Thanks

Neal

[stevieturbo]

A simple mechanical/visual check will let you know if both turbos have the ability to work. They are quite simple devices.

But any more info on holding back ? Is it just flat, rich/lean ? missfires ? What cam, springs ?
Is boost steady all the time, does it fluctuate ?

[neal1980]

Hi Steve,

Car feels great below about 4k but just feels flat like your hitting a brick wall doesnt want to rev and I ocassionally get a back fire. Spoke to the rolling road guy who thinks it might be fuel pressure but runs fine up to this. I replaced the fuel regulator with a BMW one which is 3 bar 1:1 (supposidly)does this sound feasable?

Cam spec is as below, I have dual springs from Real Steel also. Was going to use there Turbo cam eventually but didnt think this one would be too bad to start with.

DW252 Viper Cyclone

Rpm Range Idle-5500rpm

@.050" In.206 Ex.206

Lift-1.60 Rockers In;.433"Ex; .433"

Lobe Sep 108 degrees

I have tested both wastegates with some compressed air and they seem to crack at a very paltry 3psi so with a MBC I have 5-10 and it seems to hold this very well. Exhaust is free flowing with no cats, I have 2 big cone air filters down the front. I have cut down trumpets in the plenum. The motor is around the 8.0:1 compression from memory. I havent checked the fuel yet as my cigarette lighter didnt work but have that sorted now I could probably do a datalog or something.

Many Thanks

Neal

[Pumaracing]

The rolling road guy "thinks" it might be fuel pressure but doesn't actually know even though it's just been on his rollers? Is he related to the people who run the machine shop in the other thread I've just commented on I wonder?

If it was running out of fuel you'd figure it would be blindingly obvious on the rollers from the gas analyser readings or does this guy deduce the A/F ratio of the cars he sets up by smell or some sort of psychic ability?

Anyhoo, it could be all sorts of things but your symptoms are certainly classic ones for broken or otherwise faulty or incorrectly installed valve springs generating insufficient fitted load. Rolling road guys, or at least the inexperienced ones, never pick this one up until they've seen it a few times because they don't actually necessarily understand or build engines themselves. They think everything must be fuel or ignition related because that's what they spend their time working on.

Do a compression test too.

and read this!

http://www.pumaracing.co.uk/diagnose.htm

[stevieturbo]

neal1980 said:

I havent checked the fuel yet as my cigarette lighter didnt work but have that sorted now I could probably do a datalog or something.

Many Thanks

Neal

Are you saying the dyno guy wasnt checking fuelling either ?

Any mild cam with little or no overlap should be safe. If you have dual springs and relatively low lift, which you appear to have, I doubt that is the problem. Plus you arent using big boost for it to have much impact on spring required.

But you need to establish if fueling is sensible, if there are missfires etc and of course where your timing is at.

And there is no reason to change the FPR. As Puma says, with an aftermarket ecu you can adjust fulling all you like. So virtually any FPR will work. All the better if it is boost referenced of course, but 99% of FPR's are capable, as they already have a vac reference. Same odds really.

Will the engine rev with no boost ?

[neal1980]

It revs fine on the spot.

Went out for a 20 mile datalog last night. The timing on boost less that 10psi is at 14deg. Assuming 1deg for every 2psi I would of expected this to be around 20-22?

What symptoms would very low timing have?? Could this be holding the engine back?

Fueling seems to go down to 11.0 - 11.5 on the wideband.

Thanks

Neal

[stevieturbo]

There is no generic x psi per x deg of timing. The engine is either tuned or guessed.
Guessing is not ideal

If you dont have access to a dyno, then the only real way is to advance timing until detonation is heard, and then step back a degree or two.
This approach certainly isnt perfect, but in many cases it will yield good results. And is certainly far better than just guessing.

Excess fuel and retarded timing certainly could make it lethargic up top. If the wideband is correct, you certainly dont have excess fuel, so perhaps there is plenty of room for improvement with the timing. Only way to find out is to try.

[neal1980]

It was on the dyno for a few hours, going back friday so will see then. Would I be losing alot of power and heating things up with not enough advance??

Sent a datalog off last night and was suggested I should be at least running another 8 degrees at WOT on the boost im running with no problems at all.

[stevieturbo]

neal1980 said:

It was on the dyno for a few hours, going back friday so will see then. Would I be losing alot of power and heating things up with not enough advance??

Sent a datalog off last night and was suggested I should be at least running another 8 degrees at WOT on the boost im running with no problems at all.

You're back to guessing. If it was on the dyno already for several hours, why hasnt timing been omptimised ?

The timing isnt incredibly low, but absolutely retarded timing could cost tons of power.

[neal1980]

Ran out of time in the end due to other electrical problems taking up most of the day. Hopefully have a good session this Friday, its gotta make 400hp!

Its def never going over 14deg on max boost just been through the logs. Running around 10psi on low comp 8.0. I hope it gives it a kick up the arse!

[Pupp]

Not sure whether this all goes out the window with forced induction but RV8s are generally reckoned to make best torque/power at around 28deg BTDC all in.... start using long duration cams and it seems that can be pushed a bit further given the overlap effects on compression offsetting det etc. Like I say, maybe that doesn't hold good with a pressurised inlet but if it does, then you do seem a bit short on the advance front in comparison?

Again in the normally aspirated world, ignition that is too retarded will increase heat in the chamber.

Maybe a silly suggstion but it's not something daft like a wrong value in the soft-cut rev limiter field is it?

[stevieturbo]

There is no generic timing that any engine will make it's best power or torque.

Every setup will be different, CR, cams, headflow, turbo, fuel.

You'll just have to try it on the dyno and see how things go with timing. Certainly at that CR and only 10psi, yes there probably is a lot more scope for improvement.
2-3 degrees can make a huge difference, so if you were able to squeeze another 8-10 into it safely, the difference will be massive.

[neal1980]

Not the rev limiter been all through the settings. Hopefully my 8-10 degrees Im missing will give me some more.

Really difficult to explain what its doing but just wont rev up nice after 3800 really feel hardly no power being produced after this I held it there a few times and got a backfire. At start of boost its around 20deg timing and feels great then slouch

[Pupp]

stevieturbo said:

There is no generic timing that any engine will make it's best power or torque.

Every setup will be different, CR, cams, headflow, turbo, fuel.

You'll just have to try it on the dyno and see how things go with timing. Certainly at that CR and only 10psi, yes there probably is a lot more scope for improvement.
2-3 degrees can make a huge difference, so if you were able to squeeze another 8-10 into it safely, the difference will be massive.

Which part of 'generally' and 'around' did you fail to read? I wasn't suggesting the figure was a definitive value for this application but was simply putting information before the OP that originates from rather more authoritative souces than a chippy bloke on the interweb

Edited by Pupp on Monday 23 May 21:54

[neal1980]

Im grateful for any advice. Dont want to spend money if I dont have too more for the beer fund Its a long slow learning curve for me been playing with datalogs / tunerstudio and viewer tonight and its sinking in now more than ever.

I want to tinker now and do another log.....new engine needed soon probably now

[stevieturbo]

Pupp said:

Which part of 'generally' and 'around' did you fail to read? I wasn't suggesting the figure was a definitive value for this application but was simply putting information before the OP that originates from rather more authoritative souces than a chippy bloke on the interweb

Edited by Pupp on Monday 23 May 21:54

How much experience with turbocharged engines do you have ? And how many turbocharged V8's ?

I'll throw a wild guess out there and say Ive just a little bit more real world experience than you ?

Throwing a wild timing figure out there and suggesting someone aim for it is just reckless and very uninformed.
And the only chips here are the ones I eat.

[Pupp]

stevieturbo said:

Throwing a wild timing figure out there and suggesting someone aim for it is just reckless and very uninformed.

So, care to point out exactly where I did that from up on your soap-box?

[stevieturbo]

Pupp said:

So, care to point out exactly where I did that from up on your soap-box?

So how wide a scope and in which directions does "generally" and "around" offer ?

10deg either way ? 20 deg either way ? 30 deg either way ?

And with what general fuel and around what CR ? And what boost level ?

[Pupp]

stevieturbo said:

Pupp said:

So, care to point out exactly where I did that from up on your soap-box?

So how wide a scope and in which directions does "generally" and "around" offer ?

10deg either way ? 20 deg either way ? 30 deg either way ?

And with what general fuel and around what CR ? And what boost level ?

No, thought not.

Having met Neal and discussed his conversion in some detail whilst looking over his car, I'm pretty comfortable he knows exactly what was being said. Context is everything

[macdeb]

I'm sure he's grateful for any feedback.