Strange Dyno Day....

[Jon Powell]

Ok, I got my latest project on the dyno yesterday only to find something funny...

At about 4600, power drops off like a ROCK...I am talking a 50 wheel torque drop off and 25HP drop off. Torque never fully recovers & HP recovers at about 5400. at around 5600 I have another bad dip. The AFR's are steady between 11 & 12 from 2600RPM to 6700RPM.

I will post dyno plots later once I get to a computer with a scanner, but this is VERY curious.

Mods are:

RB25DET into S13 chassis

SSPower crap manifold

Innovative turbo GTS61HP

Innovative Progate wastegate

Greddy intake manifold

Q45 TB

FMIC

Sard 850cc/min injectors

Greddy 1MM Headgasket

Nismo Fuel pressure regulator set to 43.5PSI base

Greddy Profec B Spec II Boost controller

2.5" dump pipe & 3" exhaust(Had to clear the steering)

Any insight as to how we can fix this would be GREATLY appreciated.

Thanks!

Jon Powell

[FATGTS-R]

Hi Jon,

Well the first thing that alerts me is that you have not mentioned any change or modification of an ECU.

If you do a search on "Rand R" or Rich and retard I think you might find some insight.

[4door_Sleeper]

If the AFR's are all good then my guess is the timing, As mentioned above you didnt tell us what ECU you are using. Could be time for a PFC or at least a SAFC

[shif_tea]

i'm with the above 2. Rich and retard. Time for pfc

[Jon Powell]

i'm with the above 2. Rich and retard. Time for pfc

I forgot the most important part, we are using the Power FC and I have the Commander Pro software allowing me to tune the car with my laptop.

The AFR's are under 12 from 2PSI @ 2600RPM all the way through redline. They are between 11 & 12 all the way.

It appears That the FIRST drop off is boost related. I got ahold of a few more charts from the runs and it appears that the boost spikes at 16.8PSI at about 4400RPM and drops like a rock to 14PSI at 4800RPM. It never goes above 15PSI again before redline. One thing I have to look into. I am unsure if its from the crappy manifold or the boost controller. The first drop off on the power charts are at 4600ish RPM, right after boost starts to drop off. I can pretty much relate the 50lb/ft loss to that. The 5600 loss is disturbing me. I t appears to be VVT related, I assume the VVT kicks in around that area.

Is there any way I can shut off the VVT or adjust when it kicks in on a Power FC?

[N I B]

VVT is turned on at low revs and off at about 5500.

Your tune must be out as the Turbo your using is a very good bit of kit.

Fix your boost control and review your tune.

[BH_SLO32]

Most electronic boost controllers have an overboost safety function where it will lower the pressure once it exceeds a preset value. Have a good look at the boost controller settings in the first instance.

Hope this helps.

[bnr#@]

Could be old and dodgy or cloged cat... I thenk HPI had a similar problem on the 32 GTS-T they were doing before they changed to a high flow cat

[Miller the hoon]

My e boost would spick quit bad so i lowered the gate build up pressure and now it works fine

it was set on 9psi and spicked to 13 at least

i even turned the boost up to 11psi cause ther is no spike now

power band is consistant and longer and more hp

wat can u play around with on the profect b?

james

[paulr33]

it sounds like you have an exhaust restiction. what size is the housing on the turbocharger? 2.5" dump is too small most likely. do a dyno run with the exhaust dropped and i bet all the power comes back

[Jon Powell]

it sounds like you have an exhaust restiction. what size is the housing on the turbocharger? 2.5" dump is too small most likely. do a dyno run with the exhaust dropped and i bet all the power comes back

I had no choice in downpipe size, I have no room for 3" piping where its at. Beinge that the engine is in the S13 chassis and its left hand drive, I have space limitations. I had to fit a pipe between the mani & firewall & the brake booster & engine. 3" was just NOT an option. Once the exhaust gets below the steering column it opens to 3" so we are only talking about say 12-16" of 2.5 pipe before it opens up. There is no cat in the system, straight test pipe. At first I thought the O2 location was an issue, but the AFR's on my WBO2 and the dyno's match identical.

I had the overboost protection set for like 20 PSI and the boost set at 17PSI. The boost controller has a hi & lo setting and for each one you have gain, boost limit, overboost warning & overboost reaction.

I am going to try a new set of spark plugs, a new set of coils & see what happens. Is it possible the VVT kicking off could be my second dip?

I plan on running to the shop in a bit, scanning the dyno plots & uploading them. Hopefully you guys will see what I mean & help me to get an idea of whats up.

This car is a beast, what is the max RPM for stock valvetrain ont he RB25, I am thinking of upping my redline as we are still making power at 6700RPM. The thing wants to keep going!!!

Thanks for all the help!

[paulr33]

the VVT changeover is at 4700rpm, with datalogit you can change its point.

or you could also unplug it and do a dyno run, i dont think it will help much.

i still think the exhaust is the killer. you should really do a dyno run with the exhaust dropped

[Jon Powell]

Here are the sheets, let me know what you think!

Thanks!

Edited March 6, 2006 by Jon Powell

[Sydneykid]

Here are the sheets, let me know what you think!

Thanks!

The ~4,750 rpm drop looks like a pressure leak, make sure all of the hoses and clamps are secure and there are no unused fittings that aren’t blocked off completely.

My next guess for the high rpm would be ignition timing. I would try some more advance, when the inlet cam timing changes you need to carefully tune the ignition timing to suite.

Restrictions don’t usually cause a sudden drop in power, they slow down the increase, flatten it out, or cause a minor decrease, but NEVER a sudden drop. That’s a tuning issue, boost is always the first suspect.

cheers

Edited March 7, 2006 by Sydneykid

[joh21m]

i had an extremely similar problem to ures. only diff is mine is a rb20det in an s13 chassis. i went for a whole year changing my coils packs, spark plugs, fuel pumps, timing etc...

my problem turned out being when my engine was installed there were 2 identical plugs for the knock sensors. they plugged in a plug that went to the fuse box, so there was no reading from the second knock sensor causing the ECU to think something was up and drop power. i had a look and found a plug that went to the ecu, plugged that in and hey presto all is good.

moral of that story is check your knock sensors and that the plugs run to the right palces i.e. ECU, might save you a lot of money and headaches...

Edited March 9, 2006 by joh21m

[Cubes]

Joh21m,

The PFC only reports the knock reading, it doesn't do anything with it unlike the stock ecu.

[rb26s13]

2.5" dump pipe & 3" exhaust(Had to clear the steering)

i know this is irrelevent but ive got twin 3inch dump ppipes coming off the stock low mount rb26 turbos and i have no issues wat so ever clearing the steering parts?

[Craved]

i know this is irrelevent but ive got twin 3inch dump ppipes coming off the stock low mount rb26 turbos and i have no issues wat so ever clearing the steering parts?

he is left hand drive ..

so the steering column etc would be in the way unlike like yours...

Edited March 9, 2006 by Craved

[rb26s13]

oh woops didnt relise he was from the states sorry about that

[Jon Powell]

Well, I did some work to it last night. Found a decent sized boost leak, one of the clamps had slipped off the coupler. I also took the stupid fast idle device off the Q45 TB(Forgot in my haste) and reset everything. While I was letting the car warm up to set idle speed & timing, I started hearing a screaching noise from what I THOUGHT was the water pump....but no it was from the alternator. I was tightening the throttle cable and noticed an orange glow from under the throttle body....peek around and the alternator is RED HOT and emitting an orange glow from all the vents.

I wouldnt be surprised if it was a mixture of boost leak/no power for the coils that caused it, but I have a 110AMP alternator on the way that supposedly will fit the RB25, I changed plugs, coils, IAC and will be revisitng the dyno on Sat....I will let you guys know what comes of it.

Thanks for all the help!

Jon