Most Power Through An Afm In Standard Rb25 Location

[tm_r33]

is there any reason why this turbo is running factory compressor cover? Do u have another comp cover that came with the turbo?

Im slightly confused sorry lol. Is this one of those turbos that people build from bits and sell as a high flow?

Im asuming your keeping an eye on injector duty cycle and all that. And doing dyno runs with 98?

[tm_r33]

Hmm ignore that. It doesnt sound like fueling prob. Drop exhaust at cat and do a run. Measure boost before and after cooler core. If neither give any answer id be looking at the front of yoir turbo.

[Harey]

Dynosheet in post #20 has the test with no cat or catback exhaust (dark blue).

Need to do an intercooler test too.

[Legionnaire]

76mm compressor in the factory comp cover intended for stock 67mm wheel must have nearly no duffuser left so it looses thermodynamic efficiency big time.

Try comp housing and backing plate designed for 76mm wheel and see if makes a difference (it should).

Edited March 29, 2011 by Legionnaire

[GeorgesR34]

comparing the dynosheets both of them has exact dyno correction so there aren't differences as long as the car's making the same power.

Stock housing with .82 turbine sounds like a PU high flow, It made exact power as the ATR43G3 with larger back plate and bigger comp housing. Both turbos held18psi by 7000RPMs on Stao's car. Few other members also made the 300rwkws mark on same turbo with AFM in factory position so it shouldn't be an real issue. The run I'm interested in is their .82 FNT housing back to back comparison with ATR43G3 core. that held very steady 22psi made more power and torque everywhere. Ask him to give you a trail run on it and see if that get rid of the drop. If not it would be restriction some where.

[Harey]

But you can see on Tao's car he cranks the boost up to 20ish psi and the turbo responds well and holds boost. On mine the boost drops back to 15ish psi and wont make anymore up top. He had exactly the same turbo, I saw him unbolt it from his car and bolt it to mine.

Yes the 0.82 FNT changes are very interesting, but I just wanted to get close to Tao's result first.

Good idea with a test, its just the labour effort involved in swapping turbos.

[ARTZ]

tao also has different pistons yes, also compression differences between 33 and 34, depending on turbo used lower comp tends to make better power on high boosted engines does it not ?

Just a thought.

[Harey]

tao also has different pistons yes, also compression differences between 33 and 34, depending on turbo used lower comp tends to make better power on high boosted engines does it not ?

Just a thought.

Pretty sure Tao had my turbo on before his engine was rebuilt, so it was 100% factory.

What compression differences between 33 and 34? They are both 9.0 as far as I am aware.

Interesting points though.

[tm_r33]

yer pretty sure neo is still 9:1. the differences were in the head and mainly so nissan could still meet emisions standards.

standard cams in both cars? because 33 and 34 have different cams?

[Harey]

Yeah standard cams in both. Interesting didnt know they had different cams from the factory.

[tm_r33]

yes they do have different camshaft profile. they change a fair bit between different rb25 models. specs are as follow.....

R32 Skyline RB25DE Camshaft duration 240°in, 232°ex lift: 7.8mm in, 7.3mm ex.... 32

R33 Skyline RB25DE Camshaft duration 240°in, 240°ex lift: 7.8mm in, 7.8mm ex... 33 gts

RB25DET Camshaft duration 240°in, 240°ex lift: 7.8mm in, 7.8mm ex ... 33 gtst

RB25DE NEO Camshaft duration 236°in, 232°ex lift: 8.4mm in, 6.9mm ex... 34 gt

RB25DET NEO Camshaft duration 236°in, 232°ex lift: 8.4mm in, 8.7mm ex... 34gtt

u can obviously apply these to other nissan models like stageas etc. all you need to know is if your neo or non-neo and if your turbo or non turbo.

Edited March 30, 2011 by tm_r33

[tm_r33]

gtt has less duration than gtst to close up the valve overlap and keep to emisions standards i beleive. but the extra lift was probably thrown in to still let it breath well enough.

[ARTZ]

sorry guys , I swore i read somewhere the other day 33 was 8.5...

Think Im going nuts so Ill stop trying to be helpful now

[GeorgesR34]

Neo cam shafts should be slightly better plus with the advantage of solid lifters. I noticed most of the 250rwkws+ R33 rb25det dyno readings sort of noises down after 6700RPMs while the R34 rb25det Neo engine kept on making power all the way to 7200rpms. Same with Stao's results, this seems gone better after he recondite his engine head with stronger valve springs.

[Harey]

Neo cam shafts should be slightly better plus with the advantage of solid lifters. I noticed most of the 250rwkws+ R33 rb25det dyno readings sort of noises down after 6700RPMs while the R34 rb25det Neo engine kept on making power all the way to 7200rpms. Same with Stao's results, this seems gone better after he recondite his engine head with stronger valve springs.

But that makes it more of a wtf because I have a neo engine and he had a standard R33 engine (prior to rebuild).

[tm_r33]

yer i thought 33 gtst was 8.5 but apparantly not.

its duration that will help top end majorly

[Harey]

yer i thought 33 gtst was 8.5 but apparantly not.

its duration that will help top end majorly

Interesting, sounds like a set of tomei poncam B's might be really beneficial on the R34.

Although bit pricey ouch $1199!!

http://justjap.com/store/product.php?productid=16269&cat=305&page=1

[wolverine]

Just under $800 from Nengun.

I would love to see back to back testing of the type A vs type B on a neo. Both have the same 9.15mm lift but the type A has a little less duration 252 vs 260.

[Harey]

I made 270rwkw on 98 with 17psi.

I made 369rwkw on 104 with 24psi

This was with the piping, same size as the AFM. Used an 3" -- 4" pipe to accomodate the GT30 4" intake.

A Z32 in a factory-ish position is not a restriction. If it was a restriction and now allowing the air in, it would never have made 24psi without giving issues.

AFM infront of the turbo, is not a restriction that's worth worrying about. Z32's flow enough for the majority of street setups, and have done so time over.

There are also people here with GT35's (4" intake also) who've made over 300rwkw with a Z32 as well. Check the dyno results threads and see.

The fact you run more boost without anymore power is indicative of two things.

1. Exhaust restriction or Intercooler restriction.

2. Turbo is on its limit.

Both are possible, #2 cannot be discounted until you rule out the #1 items.

That really is great info Ash, I think I brushed over it. The 3" intake stays with the Z32 afm.

My current thinking is that its a combination of intercooler restriction and turbo on its limit. If you look at Tao's result (yellow and green) you can see the turbo hitting its limit around 19psi. The boost drops off with the same curve as mine except ~3-4psi higher. Well what if my intercooler (second hand Trust item) is not working well and causing 3-4psi of pressure loss meaning that the turbo is on its limit.

I purchased some fittings to install into the hot pipe from the turbo to the intercooler so I can compare results between that and after the intercooler. I just have one boost gauge to measure so I was going to move it and get a rough figure that way. Is there such thing as a pressure difference tester?

[R31Nismoid]

no real tester as such - just gotta measure boost pre and post.

So you can do pre/post cooler, or some just do it turbo/plenum. T/P is probably better as it's an overall reading.

Bends in cooler piping and so on could be causing issues so the absolute 'end to end' test would be best.