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Questions - My dyno results ok? How to improve?


Bill
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Hi Guys,

I finally had my car on the Dyno today.

Im a little dissapointed to be honest, I thought it would be a bit better than this.

Car is an R34 GTT

3 inch Exahust turbo back

Trust Pod filter

Greddy Front mount intercooler

E-Boost at 9psi

Rest is stock.

As you can see from the dyno pic there is horrible stuff happening to the power curve.

Im lead to belive that is caused by the stock computer getting upset at 9psi of boost. This sound right?

Im getting a Apexi Power FC installed in a few weeks.

Boost will be incresed then too. Whats a safe level btw? (Ive been told 12 to 14psi).

Anyone want to hazard a guess at what improvment I should see?

Any suggestions on what else to do?

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Yeah Bill... You weren't being lied to.

The stock GTS-t/GT-t ECU has a boost cut at 10psi-ish where it retards the timing to protect the engine as it thinks something is wrong and the car is overboosting.

A PowerFC will give you a MUCH nicer power curve... Here's what happened to mine:

BLUE LINE: Standard ECU with 0.9 bar boost

PINK LINE: Power FC with 0.9 bar boost

powerFC.jpg

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As Merlis said, you have hit the dreaded Skyline overboost protection. All is good with PFC fitted and tuned. You will pick up the usual 25 rwkw max power and about 40 rwkw average power. :P

PS; get them to do the dyno in 4th gear next time, makes it easier for my poor brain to work out engine rpm. :P

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Not entirely sure what each individual abbreviation means but as I understand it, Shoot Out Mode locks certain variables such as ramp rate and drive train inertia settings and calculates the power level based on a benchmark 'standard day'. It does however list the atmospheric and ramp conditions to aid comparison with charts produced elsewhere.

I guess some of the abbrev's would be ramp rates, air temps, barometric pressure etc etc...

Adrian

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is the std ecu boost cut for a gtst 10psi??? i thought it was 12psi?

is there are difference between s1 and s2 r33 gtst and r34 gtt for that matter as s2 gtst and r34 gtt have those plastic impeller baldes and what not which ppl say that cant be boosted as much as the ceramic one even though it is ulitmately the same almost...

anyway i got s1 r33 and thought the boost cut was at 12psi, thats all....

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To compare, my gtt produces 217 hp atw with full 3" turbo back, air filter stock boost

and it produced 246 hp with the same setup but increase the boost to 8 or 9 psi and safc2 tuned

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Just to clear somthing up here. The ECU doesn't read the boost pressure correct? It caculates it from Air flow. So it is possable to hit boost cut with out running alot of boost say if you put a larger turbo and IC on. I know I have hit the cut in my car at 9 PSI.

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Yep, you are correct USRB,

It is an airflow cut, not boost cut technically. Sydneykid has corrected my terminology on this many times, lol.

Thats why you would hit your " boost cut " earlier on a cold day, with full load of passengers, with a bigger turbo, etc etc.

The ecu does not go into this mode from a manifold pressure signal, it will perform this " cut " or " overboost protection " as a direct result from signals sent from the air flow meter.

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Bill.

Don't be dissappointed.

I made about the same with very similar mods.

I had 162 with unshielded pod, bleed valve just before boost cut, full exhaust (excluding dump).

I now have a big intercooler, but that big dip is exactly what I get too. It sucks.

I'm about to get A PowerFC fitted thought, so happy days for me.

The more mods you do, the worse the dip.

Get it tuned out.

BASS OUT

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I don't mean to knock you so don't take it personally, but isn't that power figure really Poor?

I mean I got a similar figure when I had my R32 with an exhaust, filter, rb25 turbo and 11psi..

and alot of guys get over 160rwkw with stock rb20 turbo..

surely this is not normal for an R34 GTT

unless it's auto.. maybe?

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GTST

Problem being that each dyno is slightly different, sometimes significantly different.

I clocked 155rwkw on one dyno, then 126 on another, then wound the boost up and made 162 on a dyno similar dyno to the 126 reading one.

If you extrapolate the above figures you could come up with the following.

155/126 = 1.23 (different between dyno readings)

then 162 x 1.23 =199.26 (taking modded car back to first dyno)

So you could say that I have 199 rwkw if I went to the right dyno........

It's all reletive.

Look at my sig and the quarter mile time, and that should give you a better idea as to the cars grunt.

BASS OUT

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yeah the results with the power fc are good, where can you get these from and what is it that they do ?

Pete,

PowerFCs are a stand alone computer which plug straight in where your factory comp is. They run everying including air con etc... They get rid of your speed limiter, boost cut and so on and run much smoother over all. They'll generally cost between $200 and $400 to tune on a dyno with standard mods but they're about the best you can get of the money. Just had mine put in and am pretty happy with it.

This link is about the cheapest place you'll find them:

http://www.nengun.com/index.php?cPath=38_2...14e1fa8438ddc03

I bought some other bits from here a couple of months ago and they usually deliver within a week.

Good luck.

Adam

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A very stupid question, because I'm 99% sure the answer is 'no', but an S-AFC won't help will it? Or will it help smooth things out even though the stocker ECU will still be enabling the boost cut?

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is the std ecu boost cut for a gtst 10psi??? i thought it was 12psi?

is there are difference between s1 and s2 r33 gtst and r34 gtt for that matter as s2 gtst and r34 gtt have those plastic impeller baldes and what not which ppl say that cant be boosted as much as the ceramic one even though it is ulitmately the same almost...

anyway i got s1 r33 and thought the boost cut was at 12psi, thats all....

Let's clear something up here, R32 GTST, R32 GTR, R33 GTST, R33 GTR and R34 GTT all have ceramic turbines. R32 GTST, R32 GTR, R33 GTST, R33 GTR have steel compressor wheels. These turbos are made by Garrett for Nissan using Nissan tooling. Although I have seen a couple of late R33 GTST's with plastic compressor wheels. All R34 GTT's I have seen have plastic compresor wheels. These turbos are made by Hitachi for Nissan using Nissan tooling.

I have never seen a problem with the plastic compressor wheels, it's the ceramic turbines that are subject to failure at high boost and/or temperature.

The type of turbo fitted has nothing to do with the overboost protection, its dependant on the ECU. :P

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A very stupid question, because I'm 99% sure the answer is 'no', but an S-AFC won't help will it? Or will it help smooth things out even though the stocker ECU will still be enabling the boost cut?

An SAFC may well help, ultimately it depends on the amount of airflow. An SAFC simply modifies the voltage from the AFM to the ECU. Generally increasing the boost (from std) causes RB25's to run rich. In order to lean out these excessively rich A/F ratios, the SAFC reduces the AFM voltage the ECU sees. This "tricks" the ECU into believing that the engine is using less airflow than it really is, so the ECU injects less fuel. Hence correcting (leaning out) the A/F ratios. :wassup:

In some cases optimising the A/F ratios requires lowering the AFM voltages below that which the ECU moves into over boost protection. So you don't get the big power "dip" at ~5,000rpm. There is a limit however, around 200 rwkw has been my experience, where the SAFC can't lower the voltages sufficiently and the "dip" returns. :thumbdwn:

The best answer is a Power FC (FC= Full Computer), no more dips then, at any power level. :P

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Well, that suits me quite well... the current target is 200rwkw as cheaply (but as safely) as possible. I've cut corners by using a 34GTT intercooler, so if an SAFC can smooth out things up to 200rwkw, fine by me. :P

Thanks SK, excellent advice as always.

Edit: Additional stupid question... anyone know a good place in Sydney to get an SAFC fitted and tuned? I'm off on a driving holiday soon, and I've got some free time there...

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