turbotuner20v

I put the car on a different dyno last weekend for a car show and noticed that the power seems uneven over 5,200 rpm. I'm not really that concerned with the peak numbers since weather/dyno/ect were different, but I think it should be carrying the power better up top.

First thing I'm going to check and swap are the plugs, but curious if anyone else has ideas on things to check. I've noticed the low rpm driveability has been a little off lately as well, which seems like it could be a plug thing too.

lsxmalibu

iTrader: (50)

valve springs?

ramairetransam

iTrader: (18)

any belt slip?

9sectruck

iTrader: (9)

Blowing out spark?
Gap on plugs?
Was the car puffing black smoke when it was up in that rpm?

turbotuner20v

Cam is pretty mild w/ ~2k mile old Brian Tooley .660 springs, so I wasn't ready to go down that path yet, but maybe if the plugs and just small misc. don't clear it up

turbotuner20v

I'll try to log boost after the plug swap. I've felt bad belt slip before, and it doesn't feel like that. Seat of the pants still feels strong.

Atomic

iTrader: (37)

Most likely too much gap on the plugs. Mine like around 0.020 above 20psi.

ramairetransam

iTrader: (18)

maybe its breaking up , lean possibly .

Detoxx03

iTrader: (14)

I'm thinking plugs also.

turbotuner20v

NGK BR7EF at orignial gap. I want to say it was ~.024?

It wasn't smoking or doing anything odd, didn't notice anything till I walked over to look at the graph.

turbotuner20v

a/f seemed to look pretty good (maybe too rich). 10.6 on the widband in the car, little different by the time it hit the sniffer.

Detoxx03

iTrader: (14)

I would put 8's or 9's in it. I'm running 8's currently.

stevieturbo

Sure it isnt just a a fault of the dyno ?

Or possibly excessively fuelled ?

There is nothing on the graph to indicate lean...or a misfire as such. Unless it is mega rich, and that's causing the misfire and a leaner than expected reading...hence a fairly normal AFR reading overall.

Ive 7's in my car, really cant see a need for 8's let alone 9's. Although an 8 would do no harm.

How does the car perform on the street ? With such a flatline, it should be noticeable if there was a problem.

MaxxMitchell

iTrader: (15)

If you want to try a colder plug that seems to fire better in my opinion at that power level on E85 try the NGK R5724-9 stock number 7891. These are non resister "racing" plugs. They will also come with a tighter gap out of the box. I swap out my 7s every 1500 miles, or before each racing event.

Didn't you dyno out a bit higher on HP before, like 915rw? I have seen additional timing help smooth out the graph when it oscillates like that as well, but that depends on where you are at currently.

I'd say its in the ignition, probably plugs, possibly wires.

turbotuner20v

Not sure what wheel spin looks like on a dyno, but that's the only thing I could see being wrong with it, it put out reasonable #'s/curves on other cars.

Car still feels good, but if it's only missing 40-50whp I'm not sure I'd really feel that since it doesn't nose over, just doesn't reach the same peak.

I'm going to stick with the 7's since they did ok before (and I already have spares I've been meaning to swap).

Here's a pen and paper overlay w/ the other dyno hp curve. It's about ~25hp difference for weather/dyno I'd guess, so this should have been ~875whp maybe.

turbotuner20v

That's good to know, I have ~2,000 miles on these plugs. Figured I'd have to change them more often w/ the copper, but wasn't sure what 'often' was. I'll keep those other ones in mind too for the next plug change.

Yea, it did 915whp on Justin's dyno back when it was cold out. I think I'm around 16* advance.

ajrothm

First thing I notice is the smoothing is set on 3, that's one reason the chart is so bumpy. Second thing I would do is change plugs, run whatever you want in it but put a fresh set in, regardless of what they look like. I recently ran into a weird running issue that would only occur at wot at high rpms, I found a hair line crack in the porcelain on one plug, it was arcing from that crack to the head. Next thing to check is ohm out the plug wires, especially if you have done a coil relocation... I had a weird miss that would develop at 5000 rpms under boost and it was one spark plug wire (brand new MSDs) that had high ohms, it was a questionable connection. Now I keep extra MSD wire in stock as well as connectors and check my ohms often.

Lastly it "could" be valve springs but I doubt it unless the springs weren't setup to the correct spring height. I have the same cam you do and run a little less spring then you have and mine pulls clean to 7200.... (Although my power peaks at 6000 and holds it to 6400, then starts dropping). Lastly is good ole belt slip.. You'll see that in your KPAs on HPT though if at slipping.

Your combo may not make power at 7000 but it shouldn't nose dive the way if does.. My guess is plugs or wires.

Look at your O2 readings(the factory O2s, not the wideband) on each bank and compare them, make sure they are tracking closely and no weird spikes or dips... If you see something there, its an ignition miss for sure.

ajrothm

One more thing, try making a pull without the inlet pipe/air filter on the blower and I bet that smooths out the curve and makes it hold on better.. My curve looks similar to yours until I pulled off the filter/pipe, I made no other change and it gained 45 HP and the curve was better, as you can see in this pic:



F series blowers don't like anything on the inlet.

ajrothm

Your Dyno guy needs to give you the numbers in SAE and Smoothing set on 5. Stick with the AFR you're seeing in your wideband, not the tail pipe sniffer. 10.6 is pretty rich.. I went from 10.6 AFR to 10.9-11.0 AFR and it gained 40rwhp. So maybe your tune is getting off some how, maybe the O2 sensors are getting wacked..

I also run the BR7EF plugs with no issues.. Just keep em fresh regardless of from the plug reading is showing you.

In theory, SAE will correct the numbers (to a degree) for crappier weather etc etc.. Yes you'll make more power in better air, but you'll have less correction factor adding in to the numbers so they should always be similar..(assuming same Dyno and SAE correction.

jridenour31

^ this.