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Well we had some success on the weekend in terms of results but the head is still lifting. Somewhat less, but still not a good thing. I think to make this particular motor work more efficiently we either have to move to a smaller turbo to get more response and have a bit less peak hp, or move to a larger turbo and possibly shorter runner intake and then make more power but have a peakier motor. None of these are really a suitable option for us.
As an aside, there were a few of those Subaru BRZ's running around the event on the weekend. One of them was pumping out 300kw's to the wheels (400whp) at 17psi from a 2ltr motor. He said that the stock versions of these motors are running 12:5.1 c/r and these guys reduced this to iirc 11:8.1 for the turbo application.
Hi Pat
I am sure reading through this thread there are many people here with far superior technical knowledge than I have to offer but for the small investment required is it not worth trying the 0.82 hotside housing as this seems like the obvious next step? Or have I missed something and you have already been there? The large compressor should be much happier breathing through this housing. Maybe you would not lose so much response and take the pressure off the head a little.
It is hard to fully understand Corleone's curves as posted in his thread. It is clear that he kept making power past the "typical" roll-off point. I am sure I am biased but I do not think my torque curve is typical as it allows me to keep making power at the top end.
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Anything stopping you from going to 7200 rpm? Your cam should benefit more.
Anything stopping you from going to 7200 rpm? Your cam should benefit more.
Rod bearings Would need a dry sump and I have no plans for that at the present time. The internals are lighter and the rod bearing are much better on a Hybrid Stroker but if oil cavitation is occurring at the input side of the pump as we suspect then rod bearing are still at risk at high rpm's.
I am sure reading through this thread there are many people here with far superior technical knowledge than I have to offer but for the small investment required is it not worth trying the 0.82 hotside housing as this seems like the obvious next step? Or have I missed something and you have already been there? The large compressor should be much happier breathing through this housing. Maybe you would not lose so much response and take the pressure off the head a little.
Originally Posted by Raceboy
I agree with nick_968. With such TIP/MAP ration you will not lose turbo response at all, but gain more relaxed engine breathing.
That's an option however when we had the .82 on there previously it still spat out coolant on the dyno and that was with a larger and longer Xover. Our next option is to try a thicker headgasket to reduce c/r. Have to work out how thick and by how much.
The nice thing about this motor is revving out to 8k. While it's definitely laggier than the old motor it does zing out nicely in the top end. Having said that our data showed that we were well down on speed at the end of the short main straight last weekend. 229kmh last year down to 215kmh. So we were well down on our previous best lap time. Much of that would be due to having to downshift to 2nd gear twice wereas previously we could rely on much more tq and stay in 3rd. I think this motor would benefit from a smaller turbo and a bit less c/r. Not sure that we will drop much more $ into it though.
Are you running rpm-based boost control? One thing you can try if you are lifting the head is knocking down the boost around peak torque (BMEP) but then rolling it back in above that. Its a bit of a hack but if you are really that close to the edge it may help it live longer.
This is a fascinating thread, and a lot of information has been shared. Reading somewhat between Patrick's lines, I suspect he's trying to determine if the (very high) TIP is somehow responsible for the lack of anticipated power. Good and pertinent information has been presented by Thingo's #23, Geneqco's #24, Raceboy's #33, Geneqco's #35, and Duke's #42. These posts, I believe, address Patrick's issue.
Patrick, work on the TIP/Boost ratio. There's no reason you can't get very close to 1:1 with a modern and correctly sized turbo. You'll be rewarded with lots of power with your big cam and head, and big power much higher in the rev range. I suspect the only component change will involve the turbo. Your head lifting issues will likely disappear too.
For the moment I'm not going to spend too much more time/money on this motor. I'm trying desperately to pull a 16v larger motor together to get us to the main event later this year. Having said that Michael, if we went to back to the larger .82 housing I wonder how much effect that would have on backpressure? And how much effect would it have on response? At this stage even with our current setup, it's too laggy. Freeing up the backpressure with bigger turbine housing would seemingly exacerbate this. As a matter of interest I'd like to try a few other options but budget is having the biggest effect on my program.
As weird as that may seem, if a given turbine is too restrictive for given motor at given rpm range, going larger turbine will cure many issues and the response will actually be better.
It's a two way system: engine affects turbocharger and turbo choice affects engine breathing which itself affects how turbo will spool.
We experience this with my friends 3.0 8v. He had GT3582R with .63 turbine and TIP spiked heavily after max torque range was passed. He changed to .82 and boost response actually improved while gaining 35 Nm in the upper rpm range without any other modifications. Later the less backpressure allowed to use more ignition advance -> more power.
Interesting... I thought as much and suggested before that the .82 may get pretty close to the power level with the 3.1 due to my suspicion that the .82 housing may have become somewhat of a limiting factor for the 3.1 l at that power level.
I think the extra 35 Nm your friend experienced would get uncannily close in Patrick's case... always nice to have real world hard evidence to back up one's theories!
06-15-2015, 05:27 PM
but I do not think my torque curve is typical as it allows me to keep making power at the top end. 
