Boosted Performance round 2 list

m3chhawk

Just out of curiosity, why didn't you use the boost controller?

GaleForce

We did use the boost controller. High boost is with the boost controller and the low boost is just waste gate springs.

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m3chhawk

What was the controller set at?

Boosted Performance

Just to touch on that....


I will be doing a test on the next local dyno tune comming up in a couple of weeks here to figure this boost thing out.

I have done a lot of research, and it seems that the 1.32 a/r housing may just be optimal for these engines in the high RPM's. The dyno Gale posted is with the 1.15 a/r housing, and it still spools VERY fast. Because it does spool so fast, the turbine may still be a bit of a restriction in the upper RPM's. It makes perfect sense, but needs to be proven. To do this, I will log the EBP (exhaust back pressure) on the identical housing for a local tune with the 1.15 a/r housing. This is the exhaust pressure just before the turbine housing inlet (not after the turbo). This will give me (and I will share this as I do everything) a solid idea of what is going on, and if a larger turbine is indeed the way to go. This was my suspicion with with the 1.0 a/r housing, hence the upgrade in size. It did not work out as I had anticipated.


This engine is very efficient, and flows so well (and a lot) in the 6,000 to 8,000rpm that these (smaller) turbines may be a bit of a restriction. I have spend a lot of time trying to figure this out. I have also talked to a couple of shops that run these turbos on stroked 2JZ's, and they are making 700whp with these turbos and the 1.15 a/r housings. The guys are also saying that they would not even think about going to the 1.32 a/r housings as they are "for V8's". I am starting to think that the 370z engine at 7,500rpm flows a lot more than a V8 at 5,000rpm (for example). I also have a customer making 580whp with the identical twin scroll kit on a 350z, and the boost is solid from 3,500rpm to 7,000rpm on a 350z. But then again, on the VQ35, there is no point of going any higher with the RPM's, and there is a 200cc displacement difference.



It seems like the boost holds just fine up to about 6,500rpm, and then falls a bit after that. I am not sure why the EBC is unable to hold the boost steady/flat. I will get to the bottom of it, and as mentioned will report back.

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m3chhawk

Theoretical volumetric efficiency numbers:

LS1 at 5,000 RPM: 501 cubic feet per minute
LS1 at 6,000 RPM: 601 cubic feet per minute
VQ37 at 7,500 RPM: 490 cubic feet per minute
2JZ at 6,800 RPM: 360 cubic feet per minute

So assuming even a slight bump in volumetric efficiency for the VQ over the LS1, you are in the upper operating ranges of an LS1 and 25% more than a 2JZ

XwChriswX

It may not be a similar problem as it is boosted vs N/A, but I am having a similar problem with my LTH's. In the low/mid ranges, it improves power greatly, but after 6500rpms power flatlines, and indeed begins to drop off. I belive the flow of the vq37 even in N/A form is very high and the LTH's aren't able to keep up, thus becoming the choke point. This flatlining was apparent in dyno's before and after tuning. With K&N drop ins and a full 2.75" CAI.

Just thought this info might help in confirming the theory the vq37 flows a Lot of gasses in the high rpm bands.

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Bonnie - Stage 2, Audio build coming this fall!
R.I.P. Abby 3/29/10 - 3/30/14

elperuano

I have the same problem holding full boost to redline... Up towards the top it'll start droppin a little under 11 psi.

Great numbers Gale. Sure must be a blast to drive now!

Boosted Performance

What kit, or I should ask what turbine housing?

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elperuano

Stage 2 Gtm, .86

Boosted Performance

I think it is common, it's just that nobody posts dyno charts with the boost curve. Or at least it is very uncommon.

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elperuano

It's common, just don't think anyone has figured out how to hold it steady to redline. My chart is posted in the sticky FI finished builds. But no boost chart jus hp/tq

Boosted Performance

Thank you for sharing that info. BTW. I really appreciate it.

The reason I think it is back pressure is the fact that this thing spools stupid fast. If it spools fast, you will get great low end/mid range as is the case here. But for that to happen, the top end may suffer a bit...again the case here. So if I open it up with a 1.32 housing, the boost may slow down a bit, but the boost along with mid range/top end would be much better. Not that it is bad at all now...I just like it perfect .

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Mr.Squeeze

This is very interesting that boost falls off in the upper rpm's .With my car my boost holds well all the way to red line but I am experiencing backpressure.

What kind of boost controller was used?.

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Driven Motorsports Single Turbo 7675 T4 1.32 A/R 995WHP 780TQ

ENT-Z

Jason has the same controller as me, HKS EVC-S.

Mr.Squeeze

So we all have the same boost controller Gale and my self got tuned by the same tuner /same dyno

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Driven Motorsports Single Turbo 7675 T4 1.32 A/R 995WHP 780TQ