3076r On 26/30 Dyno Results And Possible Issues

[unique1]

hey guys i been reading the 30 forums for a fair while and recently finished a throw together engine for abit of fun and see how the 30 performs compared to my old rb26.

I bought a stocker n/a bottom end from a mate for a carton and pulled it apart and ring gaps were shocking (like double the gap it should have), but bearings were pretty decent and motor had been rebuilt in 1998 so i just put it together. The rb26 head is a recond dead stocker with no porting or mods at all. I am using a 1.2mm hks metal gasket i had lying around as well. Comp test showed all cylinders are within 2psi and around the 150psi range so its pretty low comp ratio i reckon.

I threw on a brand new gt3076r 56t with the 0.8 v-band housing and a custom steam pipe manifold (used to be on Fatz old r31 actually) and a hks 50mm gate i had also lying around. Its got a 3" exhuast with a 3' used high flow cat and small centre muffler with internal diameter around 2.5' or so and a rear magnaflow 3.5' cannon (pretty much whole engine is using bits i had sitting around).

went to the dyno on friday and threw it on, ran great once we sorted a dead coil and idled smooth as silk The tuner played around and did the offboost stuff and mentioned he had trouble keeping it off boost anything around the 2000rpm range it just wanted to scream on lol. We put boost on gate pressure (12psi or so) and it made around the 270hp range, then upped it to 17psi and managed 315rwhp (dyno is very low reading, on other dd dynos ive gained another 40hp or so, so its around the 345-350rwhp range).

We noticed it climbs real nice upto 5000rpm and then dips on the curve and then slowly goes back up to 6800rpm revlimit. When we added 2psi boost it would gain 30rwhp just under the 5000rpm area but by the peak power rpm it only gained 4hp.

any ideas on what it could be? afr's stay spot on through the rpm range and so does the boost so im thinking its the cat, or muffler or even the turbo is just too small and cant push much more up the top but the boost increase just pushes the midrange power up.

anyone seem something similiar with restrictive turbo/exhuast setups?

I was hoping for around the 360rwhp range on this dyno but it seems to have hit a brick wall and more boost is giving bugger all gains.

im thinking gt3582 time already and i only just got it tuned. I only drove it for 20 secs because its currently in an unregistered car.

Edited December 9, 2008 by unique1

[bubba]

The 2.5" section isn't going to be helping at all but I don't see how it would recover and keep making power if it was a restriction..

My exhaust housing is my restriction and when that noses over, it does so rather hard and doesn't recover itself..

First step is probably cut out that centre muffler and replace with a piece of 3" pipe and see how it goes from there.

[Pattygtst]

should try another dyno too, see how accurate the figre is in comparison.

Should be making heaps more power on 17psi. Most probably an exhaust restriction, you should have a power run with the exhaust dropped.

[Adriano]

Another dyno isnt going to help, Could there be an issue with valve float? I would just drop the exhaust at the cat, and give it a run. Are you running a screamer?

Edited December 10, 2008 by Adriano

[Al]

That's a pretty strange/poor graph; what yours is making in hp i'm making in kw. Even the curve itself is not what i would expect from the combination.

I personally would look at the exhaust system and remove anything smaller than 3", as this would definately have a -ve effect throughout the whole rev range, even replace the cat with a 3" pipe, just to test how restrictive that particular cat is.

With my previous rb25/HKS GTRS setup my old exhaust was causing the turbo to act like a big top mount; had sooo much lag then everything at a flick of a switch. Replaced the exhaust and cat and gained soo much low-mid range torque and power that the tune jumped into another load band on the ecu.

Below is a graph of my current rb30/rb25 setup using a Garrett GT3076R turbo with a 0.8# rear housing. The exhaust is back to the first system i had, but with the "cat" from the second exhaust systems. I prefer this exhaust because it has two mufflers and a 12" hotdog, and is pretty quite, but i will later change the exhaust and do another dyno run to see if any gains could be had.

[unique1]

thanks for the comments, i been thinking about it today and my mate used to own the exhuast manifold on a rb26 running a gt3540 from a xr6t and only ever managed 360rwhp on 24psi or something, so i think mani isnt helping at all. Valve float with a rb26 head is unlikely. The exhuast will be dropped first with the cat left on and see the difference, and then ill unbolt the cat too and try it. Its running a screamer yes. I want to drive it and see how it feels properly but the cars not to be drivin on the road, ill get a permit on weekend and drive it for abit and see how it feels.

I have to add on a couple of the dyno runs it suddenly didnt dip power at 5000rpm at all and then last few it did it again so something is playing up, afr's stayed the same on both runs and boost was spot on the whole way.

i also did a leakdown on the motor last night and it isnt exactly healthy...

29%, 29%, 20%, 27%, 27%, 30% are the leak results, so its definately not good. Wish i put new rings in it while it was apart

i also checked the base timing and it was on 10 degrees when ecu said it was supposed to be on 20 degrees, so that means when at fullboost it was only on like 7 degrees, ill have to dyno it again and see what happens

Edited December 10, 2008 by unique1

[R31Nismoid]

Exhaust is a simple thing to check, drop it from the end of the dump before the CAT.

That will easily tell you if thats the problem and will take 5mins.

Is the gate venting external or not?

Have a crack and post up how you go. (edit: i see your going to drop it, good-o)

The drop and then recover can occur with a restriction, where its recovering too is using less air vs what it should be @ that given RPM, much less.

Its well behind where it should be (at least another 40-50rwhp if not more), because if you arc from the 105km/h marker it should hit the 340-350hp mark @ 135km/h (where its only 300), and then noses over once again as its catching up right near the end...

Obviously thats only a very rough estimate, could go either way but that is what you'd very roughly expect once power is on - that the curve to keep climbing in a similar fashion till it flatens off a tad.

[unique1]

cheers ash, ill try and get it down to dyno when i get some spare time.

I just noticed on the fuel map also that above 5500rpm its getting less fuel than at 5000 and 5500rpm so that means its really restrictive above 5500rpm.

[unique1]

sorry for 2 posts in a row but i cant edit the one above now.

AL what is low and high boost on your dyno graph and are they both on 98 pump fuel?

mine follows very similiar until that dip and then it dies out after 108kmh

[R31Nismoid]

Al's is definitely PULP (98) - its a top notch setup.

[Al]

Thanks Ash.

High Boost:

Low Boost:

The turbo has a 15psi internally gated actuator.

The head has been ported and also has a pair of Tomei Poncams (series 1 type). Not too sure how my head compares to a std rb26 head, but i think there wouldn't be much difference.

[Pattygtst]

^ al i currently have the same turbo being put in mine, there going to use the actuator from the stock turbo. Do you think this might be an issue?

Edited December 11, 2008 by Pattygtst

[NYTSKY]

Very low reading indeed. Something a miss there.

Thats only 230RWKW @ 17psi

I made 293RWKW @ 17psi on a basic run in tune. (RB25DET)

[unique1]

i know its not right, i also know this dyno is very low reading (as i said this 315rwhp figure would be 350rwhp on any other dyno dynamics dyno in Perth), still way too low but.

cheers Al, great results if mine was anywhere near that i would be happy, i am running the external gate version too so boost should be pretty stable.

[Al]

^ al i currently have the same turbo being put in mine, there going to use the actuator from the stock turbo. Do you think this might be an issue?

A new quality actuator will give you better response and control boost better too.

The factory actuator will work, but the spring may be a little weak, causing exhaust gases to "leak", resulting in poorer response (making it more laggy) and the power to feel doughy.

[wolverine]

i guess the relatively low boost reading from your dyno Al (relative to the power output) indicates pretty low restriction to flow from the headwork and the cams.

is the high boost reading where the turbo stopped making power?

[AD4M]

micks dyno?

[Al]

i guess the relatively low boost reading from your dyno Al (relative to the power output) indicates pretty low restriction to flow from the headwork and the cams.

is the high boost reading where the turbo stopped making power?

If you look at the high boost, torque and boost curves and compare it to the low boost, torque and boost curves, you could see that the turbo is choking itself and has past it's efficiency flow rate, thus the boost and the torque start falling off. It is due to this that we did not push any harder or increase the boost any more. Things may change a little when i do my exhaust swap/test, and if i can get the turbo to hold boost on high, just like it does on low, i will push it a bit harder.

Also consider the fact that the turbo is rated at 500-550hp, i am currently making 325rwkw; considering drivetrain losses, etc, i am at the turbo's limits. I have no intentions to upgrade the turbo, even though the engine has been built to handle heaps more power, as i will lose the response that makes me grin from ear to ear .

Attached is a pic demonstrating the components used to achieve the good results at the current boost levels.

[Gts-t]

Hey al, your setup is very nice, do you run an internal gate turbo?

[DCIEVE]

thanks for the comments, i been thinking about it today and my mate used to own the exhuast manifold on a rb26 running a gt3540 from a xr6t and only ever managed 360rwhp on 24psi or something, so i think mani isnt helping at all. Valve float with a rb26 head is unlikely. The exhuast will be dropped first with the cat left on and see the difference, and then ill unbolt the cat too and try it. Its running a screamer yes. I want to drive it and see how it feels properly but the cars not to be drivin on the road, ill get a permit on weekend and drive it for abit and see how it feels.

I have to add on a couple of the dyno runs it suddenly didnt dip power at 5000rpm at all and then last few it did it again so something is playing up, afr's stayed the same on both runs and boost was spot on the whole way.

i also did a leakdown on the motor last night and it isnt exactly healthy...

29%, 29%, 20%, 27%, 27%, 30% are the leak results, so its definately not good. Wish i put new rings in it while it was apart

i also checked the base timing and it was on 10 degrees when ecu said it was supposed to be on 20 degrees, so that means when at fullboost it was only on like 7 degrees, ill have to dyno it again and see what happens

Brad, with that manifold I made 370hp at 1bar here in perth, so only 15psi, it made 396 on jem's dyno in Sydney (was running your cat in sydney, but was removed for the dyno in perth). The only draw back I can see with that manifold is the small id runners....

Very suprised you guys didnt check/set base timing!!?

Adam, yeh Mick.

Edited December 15, 2008 by DCIEVE