what's limiting my power?

[whynot]

Hi guys

I have been trying to hit 240kw atw in my corolla and so far it keeps falling flat at about 210kw and so far nothing has made a significant gain. I recommend looking at my build thread if you need more info. But I'm looking for people's ideas and their thoughts on what's going on as I have not been able to find anything similar.

Engine basics.

4agze 8.0 to 1 comp
Silver top 20 v head
Kelford cams 265deg 8.5mm lift? (194ta)
Mitsi Td05 16g turbo
3 inch turbo back exhaust

here's 3 dyno runs from just before the cams went in. There is low boost, high boost and where we adjusted the waste gate which is the highest power run.

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the dyno plot with the cams looks the same except the boost comes in a lot sooner which makes it hit 210kw sooner and not go any higher.

To start with we suspected the old 2.5 inch exhaust was a choking point so that was replaced with 3 inch. Then I put new valve springs and kelford turbo cams in it which made it a whole lot more fun to drive but no higher peak power.

A few people have mentioned it could be a restrictive intercooler or intercooler piping but my logic on that is that would just pose a restriction on the power and it could be overcome by increasing the boost until the limits of the turbo is reached and not cause a power curve like the above.

I am wondering if the nasty cheap air filter I had on it could have been causing the problem. Don't worry about what I had but let's say it is the bottle neck. Would I be correct in thinking the turbo is be essentially "cavitating" and unable to draw any more air into the engine, this could limit the peak power like I am seeing on the plot? I suppose this would be similar to running a turbo restrictor.

I am also wondering if it's the turbo running out of puff but that would also produce diminishing power gains rather than a flat line right?

Any ideas or experiences you can share would be appreciated.

[Vertigo]

Have you done any head work? Power is made by improving flow into and out of the cylinders. After that, look into improving the acoustics of the intake and to a lesser extent the exhaust manifolds.

[thegreatestben]

Doubt it's going to be the head.
I'd say it'd be the turbo. My small port 7agte peaked at 222kw with an evo 4 TD05

[whynot]

It's had a good clean up on the head but nothing major. I did consider the intake plenum but I figured that would come under the category of being able to wind up the boost and still see gains although diminishing past a point.

I'm kinda hoping it's not the turbo as I don't want the hassle of reworking things for a new turbo unless there is a bolt on upgrade in which case I'm all ears.

If the turbo is at its limit wouldn't that mean the boost would drop off even if you try to run a higher setpoint? It had no problems running higher boost.it just makes no difference to the peak power. 17psi or 21psi makes the same power. I would be interested to see a dyno graph of a turbo running below, at, and an attempt at above the limit so I can compare.

[matt dunn]

Have you logged inlet air temps?

If the turbo is near the max limit, more boost may not make more power,
as you can have the same amount of air still going into the engine,
just the air is hotter so takes up more space so the pressure rises.

Other option is the turbo is too small and restricting the flow out of the head.
Have you checked exhaust manifold pressure between the head and the turbo?

[whynot]

So a turbo at its limit can in theory move more air but not enough to overcome the air running at a higher temperature and the fact it shrinks when it cools down again?

I have not measured pre intercooler Temps or turbo back pressure but both will be easy enough to do in my case so I will do that next time it's on the dyno.

Post intercooler Temps don't go any higher than 45 deg on the dyno but I take it that pre intercooler will tell me a lot more info.

[thegreatestben]

What type of td05 are you running? Early style 1-3 or 4 onward? Shouldn't be hard either way to fit an upgrade the same type.

[whynot]

Running the early evo1-3 turbo. As for upgrades there seems to be some debate as to if the td05h is the same as a td05 or if it's a high flow version. Otherwise I would be looking at a 18 or 20g if they fitted in place of the old one. I'm trying not to modify the exhaust and manifold side of things if possible.

[Lith]

I'm kinda hoping it's not the turbo as I don't want the hassle of reworking things for a new turbo unless there is a bolt on upgrade in which case I'm all ears.

These guys make some awesome turbos, and have been weapons in the Mitsi aftermarket scene for ages now:
http://store.forcedperformance.net/merchant2/merchant.mvc?Screen=PROD&Store_Code=FP&Product_Code=NTDSMFP68HTA&Category_Code=DSM-Turbo

If the turbo is at its limit wouldn't that mean the boost would drop off even if you try to run a higher setpoint? It had no problems running higher boost.it just makes no difference to the peak power. 17psi or 21psi makes the same power

Mentioned at Toyspeed last week... particularly if your exhaust side (either exhaust system, or turbine wheel/housing or a combo) is the prime restriction then you can raise boost and not really gain anything, it basically sends exhaust pressure up at a rate which matches the intake pressure so your boost can go up but your VE drops in response and keeps life shit.

[whynot]

It sounds like the turbo is not up to the task then. I thought it would be capable of a bit more than what's it's doing but the current numbers fall pretty close to thegreatestbens figures.

I will start looking into options that will let me avoid welding stuff to fit.

Lith, I had a quick look at that site and they certainly look to have some awesome stuff, will be looking closely at what they have that's for sure.

[4agtepwr]

Turbo. With out a doubt.

[Akane]

I'd say turbo as well, especially if you have a small turbine housing.
You can try clipping your turbine side if you don't want to change your setup, but you'll lose a lot of spool for not so much gain, but others might disagree.

[CAMB01]

Turbo id say.
Those turbos are good for 240-250kw atw on a 2.0l so your 1600 will struggle to make more power.

[whynot]

Yeah I agree fully. Looking at a replacement turbo now. Probably something like the one Lith put the link in for. No mods required to anything and still being a td05 it will hopefully retain close to the quick spool the current one has. I was considering larger still but my end goal is 240kw and going too large would create unnecessary lag. Also any more power than that would be a bit pointless as 3rd gear only just gets traction as it is.

[Tranquil]

fwiw the early Evo turbo's are all different

Evo 1 turbo = 'small 16g'
Evo 2 turbo = 'big '16g'
Evo 3 turbo = 'evo3 16g'

[whynot]

I have been reading up on the turbo specs and what I have is not a standard Evo 3 td05. It looks to be some bored out unit with larger compressor and exhaust wheels. Not hugely different but definitely not standard, well according to what I can find anyway.

I will keep working on it and let you guys know the outcome.

[Dell'Orto]

Probably a bit of hassle to swap turbo flanges now, but ATA|'s setup made the power you're after with relative ease

viewtopic.php?f=29&t=81064

[Lith]

I have been reading up on the turbo specs and what I have is not a standard Evo 3 td05. It looks to be some bored out unit with larger compressor and exhaust wheels. Not hugely different but definitely not standard, well according to what I can find anyway.

I will keep working on it and let you guys know the outcome.

What details do you have about it? Have you got wheel sizes or anything? If it's in the stock turbine housing then it could still be the hold back possibly - though I still wonder if there is any engine tuning issues (either physically or in the ECU) which could be addressed from our convo a couple of weeks ago, did you try anything I mentioned?

Probably a bit of hassle to swap turbo flanges now, but ATA|'s setup made the power you're after with relative ease

viewtopic.php?f=29&t=81064

Funny thing about that is that a 16G6 compressor can technically flow the same or more than a GT2860R if it's not held back by anything!

[Lith]

I have been reading up on the turbo specs and what I have is not a standard Evo 3 td05. It looks to be some bored out unit with larger compressor and exhaust wheels. Not hugely different but definitely not standard, well according to what I can find anyway.

I will keep working on it and let you guys know the outcome.

What details do you have about it? Have you got wheel sizes or anything? If it's in the stock turbine housing then it could still be the hold back possibly - though I still wonder if there is any engine tuning issues (either physically or in the ECU) which could be addressed from our convo a couple of weeks ago, did you try anything I mentioned?

Also someone I know is on the hunt for an early model EVO turbo....

Probably a bit of hassle to swap turbo flanges now, but ATA|'s setup made the power you're after with relative ease

viewtopic.php?f=29&t=81064

Funny thing about that is that a 16G6 compressor can technically flow the same or more than a GT2860R if it's not held back by anything!

[whynot]

The specs of my current turbo is. Compressor 48.2mm/67.9mm 50 trim and turbine 56mm/49 mm 7 7 trim. AR. 70. I have no idea if this is a factory td05 or something modified as there is conflicting info on the Internet.

We have played around with the ecu tune and settings. What is programmed in there at the moment produces the best power. There is no sudden change in anything where the power on the dyno plot flattens out it just doesn't want to make any more power.

At the moment the car is getting the head skimmed and checked out as the head gasket started leaking. I suspect this is caused be me not doing that when I assembled the motor rather than associated with the current power issues.

A new turbo is really starting to look like it could fix the problem. I would like to know for sure first before I go and melt a hole through the credit card buying something decent.