Went to the Dyno

[Weatheralls Auto]

I didn't have much tuning time before hand but have the logs from dyno.

Def not the numbers I was hoping for
170.38Hp and 193.56Tq

I was making power till about 6200 when I got some big KR.

I have had to reduce spark quite a bit, I really think I can get more power with a better exhaust to be able to add more Spark again, what do you think?

http://www.scandepot.net/viewscan.php?pk=5111

[mickaz]

From my understanding the 3x00 engine are very picky on the tuning. you could have a slight thing that is not correct and loose BIG HP. me the only thing I can see is that it makes a lot of torque, is that because the engine is running rich? do you have valve springs or the lifter springs for that high rev?

[Weatheralls Auto]

just stock engine.
I raised Rpm cut off for when on the Dyno to see the numbers.

[mickaz]

so that means it was not tuned for 6000+ rpm? if you only raised the limiter, that means it was not tuned at all to rev that high. might be your prob there.
the only other thing I could see is bad gas, too high engine temp, lean condition,bad spark table and valve float.

[Superdave]

Either your wideband is off or your narrow band is off, 900mV is not 12:1 afr and 880mV is not 11:1

Based on the amount of KR i think your NB is more accurate than the wideband, that's terrible but you were floating the valves so you're lucky you didn't do any real damage.


Here at around sea level i try to get most stock gen3 engines to run about a 12.5-13:1 afr @ 26-28 degrees advance depending on the RPM. When no wideband is available i shoot for 950mV. Stock springs float around 6200 RPM so that's about as far as i let them go.

I run my 3500 up to 7200 or so with Comp 26915 springs, from 5K-7K it holds steady at 26 degrees with 0 KR @ ~12.5:1 AFR

[Weatheralls Auto]

Ahhh yes, that WB has been nothing but trouble for me!
I replace it and the NB, rewired it twice and re-calibrated it more times than I can remember!

I have it set on slowest refresh setting as when I had it on instant is was WAY OFF!

Not sure what to do there?

Do you think it could be a restricted Cat?

It is hard to see the AFR in this pic, the dyno uses the sniffer at the tailpipe (how can that be accurate? )




I did my best at a quick tune at higher rpm but as you see in 4th on the Dyno it was 133 MPH, hard to tune for that and that is another reason I was logging on the Dyno.

So I am left with 3 questions;

1. What to do with the WB to get it accurate? causes and corrections?
2. How to remove KR after 6400rpm and I only see up to 6400rpm in the bin?
3. Could a restricted Exhaust be causing both KR AND WB conditions?

[Azrael]

Use a touchless IR thermometer to measure exhaust temp before and after the cat. It should be hotter after the convertor. If it's hotter before then it's likely clogged.

Also, check for timing chain slack. Not likely with so few miles but you never know.

[Weatheralls Auto]

Ya, going to do that (ir thermometer) the chain should be good as I checked it when replacing Timing cover and only have 1250 miles since install (less than 1500 on engine itself)

Think I will also get the back pressure gauge out and check before after cat.

Oh, to add about exhaust, I am planning on a Turbo, so didn't want to spend on exhaust till then.
Right now it consists of Venture Van Downpipe and huge azz Cat (restricted maybe? )
reduced down to Sunfire Cat back then spit to 2 straight pipes.

[gar70614]

weatheralls: u think wen u get ur tune good u could help me out with mine? our cars are almost the same swap other than tranny.

[wasas9]

Yeah, You need a much better tune.

I dynoed at 205 WHP and 225 Ft lbs torque with 2.8 L exhaust manifolds and a tune meant for a 3400 in an 88 Z24

When the headers come and a little more tuning, I don't see why I wouldn't be around 225-230 WHP.

[Superdave]

As long as you don't have any exhaust leaks the tailpipe sniffers are fairly accurate although the readings are delayed and depending on your exhaust can be skewed a little. It's always best to have one closer to the engine for the most reliable results.

When it comes to widebands i always recommend the WMS unit. I've had mine for 3 or 4 years and never had a problem. It's auto-calibrating and easy to see. http://www.wmswideband.com/


Don't rev it past 6200 without upgrading the valve springs, your KR could be simply the springs floating and the pistons smacking them. You could throw on a set of LS6 Yellows and rev it to 7K although with the stock cam it's not going to make much power past 6200 anyways.

If your sig is correct then your injectors are too big and you definitely do not need an AFPR. I would swap to either a set of stock 3400 injectors or some 4.2 trailblazer injectors and run a stock 55 PSI FPR. I'm using 33lb/hr injectors and only hitting around 70% duty cycle at around 320 HP (275 @ the wheels)

AFPR's are for people who can't tune the computer like those running OBD1.5.

[3400-95-Modified]

FYI the trailblazer injectors are 63PSI at WOT, not 55... I found that out after I was maxing them out at 55PSI.

Also I helped tune a beretta thats putting down 180 at the wheels with a stock 3400 essentially and just a 282 5-speed... He also did that with the big 12" Camaro brakes on there so thats not bad.

I will recommend a PLX wideband. I have one and it's treated me well, Also does not need calibration and can be datalogged with some OBDII programs out there by adding in a serial port, very simple to do.

[Weatheralls Auto]

Thanx for the input Dave, much appreciated.
Here is where I am.

The Tuning software and files do not really have ability to specifically remove spark after 6400rpm,
However, I wont be making power up that high and no need to ever run that high again!!!
So here I am fine. (see video at end of post of her crying, I can't watch it again and wont be revin that high anymore lol)

WB and NB. I am getting conflicting info from different places, some like yourself believe my WB was incorrect and some believe my NB was.

It is really hard to see in the scan of the Dyno Sheet, but it looks like my AFR went to 12:1 about 5800rpm and held,
WB was approx 11.1:1 and NB as you saw much leaner.

So am I lean? or rich? lol

So Dave, here is something that was told to me yesterday, I would like your opinion on it as to whether it is plausible or not.

1. KR was due to Valve float or GMs over Sparking in the first place
2. depending on the Cat, the Tailpipe snipper could read .8ish leaner than actual AFR
3. Using that, take .8 from the 12:1 from dyno would equal 11.2:1 which is quite close to the 11.1:1 that my WB read
4. NB at that AFR is not accurate so rely on your WB

So if this would be accurate, then I would need to lean up a bit (which would raise kr again and have to remove spark ) this sound correct to you?


As far as injectors and AFPR, I have since removed AFPR (had issue, forgot that I had not returned yet till now lol) and am running 43.5psi (I went to the older 43.5 at this time because injectors were to big and seemed to be more stable at 43.5 rather than 55psi)

I will be starting the Turbo setup at Summers end, which is why I kept the #36
Do you think these are robbing me of some power?

Some say the 170 is not bad as, 201crank hp X .85 driveline loss = 170 but thats just stock, I want to exceed that?

Besides for leaning out AFR abit (to 12 or 12.5:1? or leaner) what else could be causing my lack of power?

I am still thinking exhaust is the issue and may not get it 100% before the Turbo setup.

Long winded post, think I covered and asked all my questions? lol

Only the sadistic should watch this, she was crying quite horribly after 6500rpm

[robertisaar]

you're running rich regardless...

i believe the theoretical ideal AFR is 12.9:1 for most power, anything more and it just doesn't burn in the combustion chamber), but a lot of things will interfere with that number. which is why i like a target AFR of 12.5-13:1...

[Superdave]

man, i cringed at that video.. The time it took to go from 5K to ~7K was crazy.


Don't assume 201 from GM is correct, with a good tune the 3500 will make 230 @ the crank easy (assuming a good exhaust and intake as well). KR is either from mechanical noise (valve float can do it) or detonation. You can pull your plugs and look for signs of detonation but i bet you won't see much.


If i remember right (and i don't run cats) the dyno i go to's sniffer was about 1.0 leaner than mine but i guarantee i had exhaust leaks here and there.

I'll post up the spark advance table from my stock 3500 tune tonight so you can see how much advance i run at each RPM, that should help a little. I'd post my VE numbers but my tune is based on 24lb/hr injectors so unless you want to do a bunch of math they won't be very helpful. haha