Disappointing dyno...what happened?

[goofynick6]

Well, I dyno'd last night on a dynojet and was a bit disappointed. I was hoping for 350whp and didn't make it.

The best theory that my tuning buddies and I could come up with was that I needed a colder plug. I'm running a 6 heat range, but they said I was crazy to not have a 7 or 8 in there. The power is awesome until 6,000 rpms where it should keep going up and up, but instead it drops off and gets kinda choppy on the chart.

SETUP: T3/T04E with .63 a/r turbine housing with stage 3 wheel at 18psi, 550cc injectors, z32 maf and tuned to a perfect 12:1 all the way across on my wideband using a custom chip. Base timing was 15 or 16 degrees, with only a couple degrees extra added in the upper rpm range. Also, I had my 3" exhaust cutout open.

On the 3rd run (red) I bumped the timing a few degrees and it helped, but it seems maybe my plugs were too hot and causing ignition break up. There's no way a turbo that size would be running out of steam at 6k on this little engine.

Any thoughts? I'm gonna get new plugs and redyno in a couple weeks when I get back from my trip home.

Large version:

http://filebox.vt.edu/users/ni...s.jpg

Thanks,

Nick

[themadscientist]

looks like wheelhop on that graph. Your problem area is at 5200, not 6000. Look it falls off consistently at 5200. Start looking for a shift in a reading at that point.

[goofynick6]

No wheelhop there

If you look at the last pull, the redline, it pulls upward till about 6k; yeah, it stops increasing so much at 5200, because the full boost has finally kicked in and isn't increasing anymore (full boost at 4500 rpms). However, I think you're looking at the torque curve mostly. It drops off at 5200 where it crosses with the hp curve.

We looked at the maps, seemed normal, the a/f was perfect.

Nick

[rb250sx]

Nick if youre comming up this way for the 4th, give me a hollar if you have time. I could use some help tuning and we can take it out for a drive:-) btw, did you ever dyno b4 the accident?

[silent dave]

it definately looks like the ignition is breaking up a bit. change plugs to a 7 and make sure they're gapped properly. maybe try closing the gap a little more too. that stuff will probably help a lot. either that or your timing map needs to be played with some more. either way you should be running at least a 7 heat range plug in there. good luck.

[Yellow4g63]

How much boost were you pushing for the dyno runs? **Edit** never mind I didn't see the part that says your running 18psi. 0n 93 pump gas.

[Ramius83]

I think changing the plugs to a colder heat range will help you out.

Too hot of a plug will result in detonation (pre-ignition) and could have resulted in your bad dyno.

Just another thought, why is your timing set at 15-16 degrees at idle? Specifically, the RB26 manual says to be at 20 degrees, is it different for the RB20?

[driftjunke]

Hmm, I would hope for a little more than 300 runing 18psi, we did the 300 at 14. You running an external wastegate, aftermarket turbo manifold? On our run we used the standard NGK V-Power for a Z31 Turbo gapped to .8

Here's my chart again to compare if you like, our setups sound similar except we're running a small IC, stock maf and injectors, and 20 base.

I like your torque on it though, closer to the HP level compared to ours, might need to bump our timing down a notch or 2.

Eric
Modified by driftjunke at 1:32 PM 7/2/2005

[goofynick6]

Yeah, the reason I was excited to dyno was after seeing your graph! I said "Well, at 18psi, 550's and z32 I should have no trouble hitting 350whp". Alas, I just meeked past your 14 psi run. I have stock manifold with adapter box and tial 38mm gate. I am going to try the colder plug, gapped to .028 sound ok? I had these plugs at .028, but maybe they were just getting too hot.

It just seems like it should have put out more than that, it feels faster.

Nick

[Carl H]

i cant belive that it only put down that much, and i really cant believe that you are pushing that much boost on a 6 heat range plug.ive always been taught that once you get to about 14psi you need to step it up a range and at about 20psi it needs another range step.try gapping to .8mm on all plugs and see if that helps, also check base timing as that can affect the whole run.

[Yellow4g63]

Do you have any boost leaks at your intakemanifold? or injectors seals?

[goofynick6]

Do you have any boost leaks at your intakemanifold? or injectors seals?

Not a one, I pressure tested to 25 psi. I am going to bump up base timing a little, reset the ecu by unplugging the battery, and put in new plugs at .8mm.

I felt like a chump when my buddy dyno'd my old KA (in his car now) with to4 turbo and made 433whp with a slipping clutch..haha.

Nick

[Yellow4g63]

LoL ouch.

[goofynick6]

Ive always been taught that once you get to about 14psi you need to step it up a range and at about 20psi it needs another range step.

Well, stock plugs are 5's, so I thought 6 would be ok, but my previous car ran half this much boost, so I guess you're right. My buddy's running 9 heat range on his SR making about 700whp.

Nick

[Carl H]

hrmmm not sure about the 5 heat range being stock, im almost postive that nissan put 6's in all their turbo cars.5 is hot for a na car, and waay too hot for a turbo car.i put 7's in this time round after boosting around on a set of 6's and it felt loads better.

[Yellow4g63]

On another note is there anyway for you to track your knock count? Since you have a chip on your ecu.

[Ramius83]

hrmmm not sure about the 5 heat range being stock, im almost postive that nissan put 6's in all their turbo cars.5 is hot for a na car, and waay too hot for a turbo car.i put 7's in this time round after boosting around on a set of 6's and it felt loads better.

Generally speaking, Nissan does actually put 5 heat range plugs into almost all their NA cars. The Maxima, KA 240, Frontier, Pathfinder, etc all have 5 heat range plugs.

The 300zx TT uses the 6 heat range plugs, ie BKR6E-11 (NGK Coppers). My RB26 came from Japan with a set of NGK Iritop (or Iridon) 7's installed, but under further investigation my motor had already been slightly modified. But after speaking with the gentleman at http://www.sparkplugs.com, he found out that the 6 heat range plugs are OEM range for turboed engines. He only recommended going to 7's when you have increased the power of the motor by at least 50 HP at the crank.

[Carl H]

Generally speaking, Nissan does actually put 5 heat range plugs into almost all their NA cars. The Maxima, KA 240, Frontier, Pathfinder, etc all have 5 heat range plugs.

lol, this i know i work at the dealer in the parts department.do you have an external gate on your setup?perhaps you are having the same problems im currently having with the turbo sucking in exhaust gas, that would severly limit your power curve.perhaps if you do have a dump pipe its not completley exiting the engine bay, where as at speed its fine?

[goofynick6]

I can't count the knock with my ecu unfortunately.

I have an external gate, but it is plumbed back into the downpipe and points right out the electric cutout down near the transmission.

My engine had 5 range plugs in it when I pulled them out at first. Can't wait to get home to fix this thing and re-dyno!

Nick

[driftjunke]

So you use a adapter plate between the manifold and turbo? We actually remove the split at the flange to merge the runners all together so that we could mount the external WG, 40mm HKS style at the back of the manifold, our dump tube is about 12 inches long and drops right below the transmission tunnel. We'll be running up to 18 this week once the new parts have been installed. Our plugs we used we're OEM Z31 turbo plugs gappe at .8

Eric

[Wulfgang]

You can't count the knock, but can you watch or log the timing? If you have a PLMS Consult device you can just log the timing during the dyno run.