RB25det cam experiences dynos suggestions

[flatrate]

Just looking for suggestions on what cams to run, seems most people run tomei's Poncam

I have searched around and havent really found any solid info on power increases with mild 400whp+ setups i know there are lots of varibles that will effect power increase, just wondering what people are getting on average with cams... they cost alot and maybe its not worth 700 bucks!!

So post up what you know...

My setup consists of

Tubular divided manifold
GT3076R with 1.06 T4 turbine housing
stock RB25 head
Built bottom end
Greddy style intake manifold
and all other supporting mods

car is only making about 411whp 320wtq at 20psi... on 92 pump...

[240slidekat]

it could be your fuel thats limiting your power, what engine management are you using?

[meet07]

411whp sounds about right. I mean isnt the 3076 good up to like 500hp? I Would be happy with 400 dude. Some race fuel and maybe 25+ psi and you would probably be close to 500. If you take out the 25% diff lost your right around 450crank power.

[flatrate]

it could be your fuel thats limiting your power, what engine management are you using?

How do you figure?

I have 850cc injectors and haltech

just doesnt seem like its making as much power as it should, i have had this same turbo on my other car a few years back and my other car did 520whp on 22psi and that was on a 4 cylinder with stock cams...

Ive noticed that the cams in RBs are pretty lame, just wondering what kinda differences people are getting out of drop in cams... tomei hks etc

[240slidekat]

i mean fuel as in the octane but that was just a guess.

[WhatsADSM]

While 411 isn't a bad number I do agree it does seem to be a little short on power... Although a drag strip mph would probably be an interesting data point. I've seen some pretty conservative dynos.

Who did your tuning? Are you sure there isn't more left in the tune?

As an aside... a 1.06 T4 turbine housing is pretty f'in huge for a turbo that isn't *that* big. Is it a twin scroll or something? Granted my car is focused on being effective on a roadcourse (i.e. I went for responsiveness), but I actually use a .68 T4 on my PT6262.

[flatrate]

i mean fuel as in the octane but that was just a guess.

It wasnt an issue but i try not to go more than 20ish psi on 92 anything more than that is really starting to heat the charge

While 411 isn't a bad number I do agree it does seem to be a little short on power... Although a drag strip mph would probably be an interesting data point. I've seen some pretty conservative dynos.

Who did your tuning? Are you sure there isn't more left in the tune?

As an aside... a 1.06 T4 turbine housing is pretty f'in huge for a turbo that isn't *that* big. Is it a twin scroll or something? Granted my car is focused on being effective on a roadcourse (i.e. I went for responsiveness), but I actually use a .68 T4 on my PT6262.

It wasnt tuned by a shop, but by a friend of mine who is VERY good at what he does... there wasnt much left, timing didnt change torque much at all and airfuels are dialed..

I used that turbine for 2 reasons... my manifold is T4 so i needed a T4 housing and 2 its an inline 6 with lots of exhuast volume.. it is a divided housing i still get 20psi by 3600-3700 easy...

trap speed would be a good measuring tool, however i dont think this dyno is wrong at all its fairly consistant, ive dynoed my other car there as well and its trap/speed is there

I dynoed there before when the engine was stock turbo, exhuast, greddy intake manifold, and 11psi... stock tune etc... it made 267whp

[meet07]

Take off the 3076 and try for a 35r. like Whatsadsm said.......the 3076 is kinda small.

[RustspecS13]

Why, there's a video of a 30R doing 500whp on a RB25 some where on this forum. I think it was posted in the last 3-4 months.

Every one just says get the 35R. Yeah well big deal,not every one using it pushes it past 500whp any way. So the 30r would probably be a better choice for them.

~Alex

[silviasgp06]

20psi by 3600-3700 and 411hp. Ide be happy, sounds really responsive

but Even if your friend is good at what he does see if you can talk to a tuner and get him to look over the tune, you never know there could be more, especially if you have made more in the past on a smaller 4 cyl. Aside from that check for power robbing issues. Maybe as stupid suggestion but check base timing again.

[flatrate]

base timing doesnt matter, the engine was tuned to maximum brake torque then taken back a couple degrees for safety, maximum brake torque is reached when additinal timing is added and minimal power is gained.. it was gaining good power 10-13wtq per degree then it vanished indicating it didnt want anymore and MBT was reached...

The 4cyl really isnt a good comparison as the cylinder head is much better than the RB's

the engine is really responsive just wished it made 450 on pump, i have a 35R sitting on my shelf in the garage im debating weather or not to put it on...

Id be happy with 500whp around 25psi... im thinking a set of cams and 5 more PSI will do it.. Just wished there were more documented power gains on cam swaps

[julio]

Just wished there were more documented power gains on cam swaps

As you quoted earlier, tomei pon cams seem to be the most popular choice. I see that you are running a greddy style intake manifold, so how high are you revving her? I would imagine (despite any hard evidence) you would benefit quite a bit from a serious cam if you're spinning it pretty high. You already have great low boost threshold, so why not go with a serious 272 setup? I'm sure you would pick up some ponies with that intake manifold and a nice redline.

Do RB25's require head modification to run cams over 9.15mm of lift like the RB26's do?

[meet07]

Just wished there were more documented power gains on cam swaps

As you quoted earlier, tomei pon cams seem to be the most popular choice. I see that you are running a greddy style intake manifold, so how high are you revving her? I would imagine (despite any hard evidence) you would benefit quite a bit from a serious cam if you're spinning it pretty high. You already have great low boost threshold, so why not go with a serious 272 setup? I'm sure you would pick up some ponies with that intake manifold and a nice redline.

Do RB25's require head modification to run cams over 9.15mm of lift like the RB26's do?

Good question....i would love to run some 272's or a set of custom 280's. Dont even think its possible with a rb25. Might have to swap in a 26 or 1j/2jz...hehe

[WhatsADSM]

base timing doesnt matter, the engine was tuned to maximum brake torque then taken back a couple degrees for safety, maximum brake torque is reached when additinal timing is added and minimal power is gained.. it was gaining good power 10-13wtq per degree then it vanished indicating it didnt want anymore and MBT was reached...

The 4cyl really isnt a good comparison as the cylinder head is much better than the RB's

the engine is really responsive just wished it made 450 on pump, i have a 35R sitting on my shelf in the garage im debating weather or not to put it on...

Id be happy with 500whp around 25psi... im thinking a set of cams and 5 more PSI will do it.. Just wished there were more documented power gains on cam swaps

Really? You hit MBT before you hit a knock threshold? Seems a little strange for 93 octane but maybe. Out of curiousity how much timing are you running through the rev-range on 20psi?

But otherwise yea I dunno what else to tell ya it does seem like in your case the engine just isnt flowing enough air to make more power. Have you checked for boost leaks? What were your IATs during the dyno runs?

[flatrate]

It was still gaining some torque with more timing, however the gains were noticably lower and the plugs were starting to show very light hints of what i thought was detonation.. could i have gotton a bit more out of it? Sure but its a street car and i want longivity as well, not to mention i tend to rape my vehicles alot. On 20psi its not running as much timing as ive seen most others... ill have to look at the map as im not sure on an exact number but its some where around the area of 12-14 degrees i wanna say... IATs where a bit warm, but theres something to consider there as well the IAT settings that haltech had in there software were off about 20 degrees or so..

[WhatsADSM]

It was still gaining some torque with more timing, however the gains were noticably lower and the plugs were starting to show very light hints of what i thought was detonation.. could i have gotton a bit more out of it? Sure but its a street car and i want longivity as well, not to mention i tend to rape my vehicles alot. On 20psi its not running as much timing as ive seen most others... ill have to look at the map as im not sure on an exact number but its some where around the area of 12-14 degrees i wanna say... IATs where a bit warm, but theres something to consider there as well the IAT settings that haltech had in there software were off about 20 degrees or so..

Good thing you were watching the plugs at least!

Yea you might have been reaching peak power due to it starting to detonate as well technically that's not MBT. I would try 2 things:

1) Put in race gas in it, and see what happens when you give it more timing. FWIW I run over just over 20* (at the top of the rev range) on e85 at 20psi.
2) Boost leak check it. I read your thread on rbfourms and you indicated you couldn't hold boost. No way a 3076r should be making 411whp, while at the same time not being able to keep up with the engine. That plus the warm IATs could definately be an indicator of a leak making the turbo work way harder than it should. (Warm air doesn't help with knock resistance either).

[Carl H]

on a 25 i'd expect abit more than 411whp out of 20psi...good numbers but like you said could be better considering your over all setup.
stock cams really do suck but its only notciable past ~6300 rpm on the 25/20...iirc the 26 is a bit higher but still runs out of puff.
whatadsm has good input, a boost leak will seriously drop power for sure...doesnt take much really from my experience even a small pinhole can mean a good 10hp (results may vary!).

[flatrate]

It was still gaining some torque with more timing, however the gains were noticably lower and the plugs were starting to show very light hints of what i thought was detonation.. could i have gotton a bit more out of it? Sure but its a street car and i want longivity as well, not to mention i tend to rape my vehicles alot. On 20psi its not running as much timing as ive seen most others... ill have to look at the map as im not sure on an exact number but its some where around the area of 12-14 degrees i wanna say... IATs where a bit warm, but theres something to consider there as well the IAT settings that haltech had in there software were off about 20 degrees or so..

Good thing you were watching the plugs at least!

Yea you might have been reaching peak power due to it starting to detonate as well technically that's not MBT. I would try 2 things:

1) Put in race gas in it, and see what happens when you give it more timing. FWIW I run over just over 20* (at the top of the rev range) on e85 at 20psi.
2) Boost leak check it. I read your thread on rbfourms and you indicated you couldn't hold boost. No way a 3076r should be making 411whp, while at the same time not being able to keep up with the engine. That plus the warm IATs could definately be an indicator of a leak making the turbo work way harder than it should. (Warm air doesn't help with knock resistance either).

technically its not MBT your right... but i reached the knock threshold, and torque gains were becoming less and less so it was close... i had race gas in it after i reached 400whp on pump... i had to stop because it would just spike and fall... i dont think it was the turbo not being able to keep up the compressor is know where near done yet i had my wg dumps recirculated back into the downpipe and i had 7 psi springs in my gates... now it has 12ish psi springs and dumps are open so well see what happends... engines power band shaped up ALOT better with the wastegate dumps open... power doesnt level off early etc.. but still simular peaks numbers...

20 degrees on E85 is completly different as im sure you know... seems most people are close to the 17 degree range but comparing timing maps means nothing... i dont think its a boost leak i think it was just s*** boost control i havent since tried to turn the boost up back up to see if it holds... altho the boost did fall off like a maxxed out compressor would...

[flatrate]

on another note, today i was driving around looking at IAT's from a 40-120ish mph pull the intake air temps SKY rocketed to 115ish degrees... ambient temp was 55ish today and it was about 65 degrees before i beat on it... somethings surely not right.

Using a GM IAT sensor, its mounted right before the throttle body; getting that hot and not even submerged into the coolant heat soaked intake manifold has got to be killing it

More to follow

[flatrate]

I found a LARGE boost leak at the blowoff valve as well as a small leak at a couple and a few injector o rings... i wonder what kinda power loss i would get with these leaks... i mean 20psi is 20psi reguardless if theres a boost leak or not right?

[l0nestar]

it makes a significant difference. Fix leaks and re-tune / re-dyno. You should be impressed.

[WhatsADSM]

I found a LARGE boost leak at the blowoff valve as well as a small leak at a couple and a few injector o rings... i wonder what kinda power loss i would get with these leaks... i mean 20psi is 20psi reguardless if theres a boost leak or not right?

20psi is not always the same.

Just like 12psi through the stock turbo is not the same power as 12psi through a GT35r.

With the boost leak your turbo was working MUCH harder to maintain the same boost level. One of the biggest differences is that when it works much harder your IATs will go up dramatically which will take away some power.

If it is a large enough leak you will likely need to retune the car a bit (Esspecially if it is still a MAF car and wasleaking after the MAF). But get it retuned and head back the dyno you will likely see an improvement.

[flatrate]

yeah it was a pretty large leak, i was regulating 20psi thru the turbo had the throttle plate open and the boost gauge would only read 13psi.. so it was leaking off pretty bad..

Curious to see what kinda power difference i wil get hoping for another 30-40whp that would put me about where im supposed to be