Tom M'Guinn

I got a last minute appointment at dynospot in San Jose today.

The car has Huntley "stage 2" turbo, Huntley injectors, Huntley Stage 3 MAF, ARC2, 3 bar pfr, stock head, stock intake, stock cam, no cat, stock exhaust, deltagate, stock muffler, Vitesse MAF chips, 100 octane, profec B at 22psi.

Since my last dyno run, I resealed the throttle body, changed to a 3 bar FPR, eliminted the venturi under the intake, changed the HG twice, changed from GURU to Vitesse chips, and down-sized the MAF from Huntley's stage 4 to the stage 3. I picked up 8 HP, and 36ft.lbs. of torque. I think most of that is from the improved a/f ratio around 5k -- still too rich, but much better than before.

The User line on the zeitronix is pin 7 to the DME -- air flow. It got to 4.3v, so looks like the MAF has a little range to spare.

Note that the a/f readings between the Zeitronix and dyno do not agree. I tuned it using the zeitronix, which shows 11:2 going to 12 across WOT (best I could do with the ARC2). But, the dyno shows that it's even richer. The sniffer came out on the first few runs, so I am a little leary of their O2 readings, but I presume their equipment is more accurate?

You could eat dinner on the torque curve. Feels very strong on the road.

fast951

Tom, Great chart. Clean up the fuel a bit and you'll have more torque.

Tom M'Guinn

On my next motor I will gladly pay you to do that for me.

fast951

You can do it now, just use the VR complete MAF kit

Tom M'Guinn

Anyone else ever compare the zeitronix to a dyno during the same run?

lart951

I ran my innovative Lm-1 with my last 3 my dynos and the lm-1 was very accurate. The reading from the shop was 11.9 and the lm-1 was 11:7.

EJ

I didn't log my zeitronix during my dyno runs (dumb) but the runs i did on the open road before and after my dyno runs showed very similar A/F ratios to what the dyno runs showed. The dyno A/F meter was put up the tail pipe.
Eric

Tom M'Guinn

They put the sniffer in my tail pipe too, but they had a hard time keeping it in for the full run -- popped out twice. On the run I posted above, the sniffer stayed in the whole time, but it made me leary of their set up. Wishful thinking maybe -- since the wideband ratios look so much better.

Keith E.

Mine showed differences were greater the higher the rpm. At 3282 rpm on the zt2 I was at 11.8:1 while the dyno showed 12.0:1. Then at 4414 rpm, zt2=11.6:1, dyno=12.0:1. Then at 6000, zt2=10.7:1, while dyno=below 10:1 (off chart, but I guess about 9.8:1). They had a metal tube that ran up into the exhaust with a hose that ran to an airpump that pulled the gasses from the exhaust to an O2 sensor. The dyno guys were impressed that the results were so close. I figured differences would be inevitable and incalculable unless you have two exact same O2 sensors. In looking at yours, I'd think you'd see a much greater dip in the power curves if their readings were correct. Good thing you weren't tuning based on their results.

Tom M'Guinn

That was my thought too ... see for example my earlier dyno sheet, where the torque is much lower with virtually all the same hardware, but with other chips that ran even richer in the middle. Note the dip in the red torque graph between 4 -4.5 where the rich mixture starts to drown the motor.

RKD in OKC

I've dynoed and logged at the same time every time I dynoed. The Zeitronix never matched the dynos sniffer, however... the dyno operator had several sniffer elements, complained about them going bad, and was not to confident in the sniffer numbers. It was usually about 1 point (1.0) leaner than my Zeitronix, ie, read 13 to the Zeitronix 12.

Ben Z.

I'd say the majority of post that I've read have reported that the zeitronix reads a little leaner than the true reading. I guess this is prefered to reading too rich, but I would prefer acuracy to an imposed saftely margin.

Also, how far into your exhaust does a dyno sniffer go? I've never done the calculations to see how fast the gas exits the ehaust, and you would have to know the time it takes to get up to max RPM on the dyno, but I assume there is an inherent lag between afr readings and actual afrs, correct? There is also probaly a lag in the O2 sensor itself, since it relies on the conduction of oxygen ions in zirconia, and this CAN'T be considered instantaneous, right?

Anyways, nice dyno, Tom!

danny951

That is quite a difference between your WB and the shop's. I am seeing sub 10 afr based on the shops setup, and 11.2 on your LM-1. Maybe try another dyno shop and see if they see the same thing?

Am I reading those charts right?

pete95zhn

I will do this within next couple of weeks,as soon as I get my car running.

BUT,if there's a leak in exhaust between your WBO2 and the sniffer,there's also a difference in reading...to leaner side,if I am correct?

toddk911

Where is your wideband located in the exhaust?

I also have Ztronics and mine is about where the cat would be.