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Discussion Starter #1 (Edited)
So I finally got to posting these numbers up, as I've been delaying it trying to figure out what's wrong with my car, lol. Anyway, before I get into it, I'll post my setup, as it's a GTE swap into an SC300. Here goes...

-Stock 2JZGTE motor (stock head, stock intake, stock pistons, stock rods, etc)
-Getrag V160 with Carbonetic triple disc.
-HKS 4 Row FMIC
-3in downpipe that Y's off into TWO, 2.5in mufflers (it's an SC, so I went for the stock "look" with the twin exit).
-GT4094R Turbo w/ .95 A/R
-Greddy exhaust manifold
-Greddy WG
-Tial BOV
-Batlground Motorsports Fuel System. with twin Walbro's, Aeromotive AFPR, stainless lines, and 1000cc injectors.
-GSC S2 cams
-Supertech Dual Valve Springs w/ retainers.
-Titan Cam Gears
-AEM EMS

Now for the problems. I seem to have a bottleneck in my car somewhere, and I'm just not sure where. The only thing I changed from before was the fuel system, cams, springs/retainers, and cam gears. The 561whp was on 20psi, on pump gas (93 octane). The 659whp was on Q16 and 26-26.5psi. The increase in power I was getting when I started to add more boost was minimal at best. I was maybe seeing like 6-7whp per psi if I went past the 25-26psi mark. Just diminishing returns. I thought that was really odd considering there are guys who are running 67DBB's and making MORE power, and with the 4094R having the 94mm exducer. I'm also running a bigger A/R than most on their 67DBB's, as I'm running the .95 as opposed to the .81 A/R. I don't really know what could cause this though. I was thinking maybe back pressure from the exhaust? I'm running a 3in DP, but would the two, 2.5in mufflers cause this? I thought guys run 3in all the way to 800+whp? Also, another weird thing was the changing the cam gear setting did NOTHING. I mean, I went as far as to advance each side like 5+ degrees, just to see, and NOTHING. It didn't move the powerband whatsoever. I just don't know what else to look for. I've even done a compression test to see if my motor was weak, but the numbers were fine. I've seen dynos on here of cars making over 700whp with a 67DBB, so maybe my turbo just sucks big time? LOL. Could the cams be the issue? Exhaust? Any ideas? Also, should the power hold a bit longer with the cams? Just curious...Thanks ahead of time!

Here's the graphs...



^^^20psi on pump gas^^^




^^^26psi on Q16^^^
 

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Discussion Starter #3
most of those cars are making 700 at 30 psi.

Making 659 @ 26 psi is good.
I don't think I would've cracked 700whp at 30psi, that's the problem. Maybe 690whp. Also, I've got a 94mm exducer, and am running a bigger A/R (.95), than most of those cars. That's why I'm just not sure what the issue is.
 

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Engmaineer
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you picked up around 100 whp with 6 more psi.

I think you would have cracked 700 at 30 psi.

When does it Y off to the 2.5 "

Is the mid pipe 3"?

If so your restriction could be at your downpipe.

A friend of mine went from a 3 inch down and mid pipe setup , to a 3 inch to 4 inch downpipe, 4 inch mid, and picked up a handfull of power at the higher rpm band.

Whats the health of the motor? Compression, leakdown, etc?
 

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Discussion Starter #5 (Edited)
you picked up around 100 whp with 6 more psi.

I think you would have cracked 700 at 30 psi.

When does it Y off to the 2.5 "

Is the mid pipe 3"?

If so your restriction could be at your downpipe.

A friend of mine went from a 3 inch down and mid pipe setup , to a 3 inch to 4 inch downpipe, 4 inch mid, and picked up a handfull of power at the higher rpm band.

Whats the health of the motor? Compression, leakdown, etc?
True, I picked that up with 6psi, but that's with race gas, more timing, boost, leaner A/F, etc. So it's not an exact comparison. I understand what you're saying though.

It Y's off right after the downpipe. It's transitional Y pipe that goes from 3in to 2, 2.5in. My exhaust is just the downpipe, Ypipe, and the back sections of 2, 2.5in exits on either side of the car.

You can't really see in this pic, but you should be able to get the idea with it being on an SC300.



The compression and leakdown all checked out fine and within specs in the factory service manual, so that's not it either. Maybe I'm just going batshit crazy! LOL.
 

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411 HP GSXR / 203 HP Vrod
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Check your piping for boost leaks. I made the same power at the same boost level and it was found that I has massive leaks.
 

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Discussion Starter #8
Dude, something is very wrong with your setup.

Slow spool, low power.


Here is my dyno from a gt42 70mm (same turbo) but journal bearing, NOT DBB. This was on a stock long block, stock cams. It had fuel and SAFC/VPC. 6 speed.

25/26PSI




You are down on power and spool. sorry. With all your mods you should have blown my #'s out of the water. The biggest concern I have is your slow spool. Note how your TQ falls off compared to mine too. I break 500 rwtq at around 4650... your above 5k.

find your bottle neck and you will probally find your lost power and slow spool.
I don't believe it's the same turbo at all actually, as the 4094R is 67.8mm compressor. As for the slow spool, I just don't know about that one, but I'm running S2's which have a good bit of lift, so that might account for some of it. Also, the TQ falling off in the comparison to our graphs is also not a straight comparison, as I rev'd my motor to 8k, and you cut yours off 6600rpm. With that said, I still think there's a bottleneck somewhere in my car, I just don't know where.
 

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Discussion Starter #9
Check your piping for boost leaks. I made the same power at the same boost level and it was found that I has massive leaks.
I checked for boost leaks, found some, and fixed them all. I fixed them with the car still strapped down actually! It didn't matter though, as I continued tuning and nothing changed. The 659whp was AFTER I fixed the boost leaks.
 

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1,150+ rwhp club
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I don't believe it's the same turbo at all actually, as the 4094R is 67.8mm compressor. e.




EDIT


I'm an idiot....

miss read what turbo you have. Thought it said GT4294 and GT4094

Sorry bro.
 

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What about ignition timing? aka "the tune" or part of it. It effects spool and power. Maybe you can compare your ignition timing with some others with same or similar turbos.
 

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Discussion Starter #13 (Edited)
What about ignition timing? aka "the tune" or part of it. It effects spool and power. Maybe you can compare your ignition timing with some others with same or similar turbos.
I don't remember the total timing I have in there, but there's room for more, I do know that. I'm not quite sure how far to the edge everyone is tuning, so that I can get a good comparison to anyone else with a similar setup. Is everyone just adding timing until the car won't take anymore within it's knock threshold? I mean, I guess I could do that, but I was just being a bit safer. Anyway, the tune is fine, but I'm more than open to comparing calibration files with anyone just to be on the safe side and see if I have room for improvements.
 

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Is the turbo in good condition? Any shaft play? The power band should not be dropping off like that.

EDIT: Forgot to add that i'm saying this because I had the same problem with my 60-1 turbo on my dsm years ago, where the power dropped off like crazy, the I switched to a BRAND NEW GT37R :) no more problems then.
 

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Discussion Starter #15
Is the turbo in good condition? Any shaft play? The power band should not be dropping off like that.

EDIT: Forgot to add that i'm saying this because I had the same problem with my 60-1 turbo on my dsm years ago, where the power dropped off like crazy, the I switched to a BRAND NEW GT37R :) no more problems then.
I haven't checked in awhile, but last time I checked, it was fine. It only has about 5k on it though, and has never been to the track, or anything like that. I can check on that too though.
 

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Have you measured exhaust manifold backpressure?

It doesnt matter if the turbo has a 100mm compressor wheel but if the exhaust housing/wheel wont flow more than 700hp, you have a bottle neck right there.
 

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Discussion Starter #17
Have you measured exhaust manifold backpressure?

It doesnt matter if the turbo has a 100mm compressor wheel but if the exhaust housing/wheel wont flow more than 700hp, you have a bottle neck right there.
I'm not sure I understand how exactly to measure this, but I thought my setup was basic enough to just bolt on, tune and go, seeing how these are all parts that have been used many times over in various other cars and turbo setups. At any rate, how do I go about measuring this?
 

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Discussion Starter #19
So is the general consensus, from those that are running similarly sized turbos, that I'm down on power and not holding power for long enough? There's not many people, if any, running the 4094R, and the 67DBB is about as close as I can get to a good comparison, so I wanted to see what others thought of the numbers.
 

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I don't like this turbo in general

Slow as hell to make boost, boost threashold is high, and it makes crap for power...; If you are looking into an alternative.., Mkumha had really good results with his BEP74R. It spools faster, has about the same boost threashold, flater curve and can put down 1000rwhp. Pretty sure with a stock long block he put down 75x @ 25/6 psi on E85
 
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