Well, it is winter here in MN, and most of us car guys are a little stir-crazy in this season (read: Comments made by myself may or may not be sane if made before spring)..... Getting $hitty with the S10 in the snow is kind of fun........... and the new indoor go-carting place helps, but it is no F-body!!

So anywho, I was looking over some data from a run I did this last fall with Moates' program on my GTA, and I noticed that I get fairly linear MAF g/sec gains through the rpm range until around 4800 rpm and at that point it kind of flounders around the 230 g/sec mark even if the RPMs increase...... So that leads me to believe that my TPI is really choking off my setup. I really didn't expect this with all of the porting I did on it - at least not at that low of an RPM - and I never really got the chance to do anything as far as logging data and reviewing it as I was laptop-less for the better part of the summer and fall....... What is also strange is that the a$$-meter sensed that the car still pulls past 5000 RPM a bit (maybe around 5300 RPM, but it is hard to say with that inaccurate factory tach ). I do have an LT1 manifold now (93 one..... still need 94-up rails and a few misc parts....) and hopefully will have that on before spring, so maybe this won't even be a factor for me for much longer......

So anyways, I am just throwing this up and kind of thinking out loud.... But feel free to throw in some input if you want guys!!

Laterzzzzz...
Matt

 

Rewire for a 730 and continue on with the fun.

 

I think my MAF reading was maxing out at 5000 rpm with a horsepower peak at 5650 rpm in the dyno, although my hp curve is quite flat from 4200 to 6000 rpm. I hope to dyno again next month now that I have the ported SLP runners and a better muffler on, although I've come close to maxing out the MAF on the street in 2nd gear (when I can get traction). Anyways, what you're experiencing is quite normal for TPI.

 

I know it is somewhat normal for a modded MAF system to max out the MAF's capabilities..... But what I am concerned about is that the MAF signal is not really maxing out, it is just plateau-ing around 230 g/sec.... I suppose there could be a calibration difference going on there with the MAF itself or inside the PROM.... but I really haven't touched the MAF scaler tables - they should be stock ARAP figures.... One would think that I could pull more than 230 g/sec - or at least that I am pulling more g/sec at 5200 rpm than I am at 4800 rpm, but the data I logged says otherwise........ ?????

Uh-oh..... I was just thinking..... Maybe the screens being removed has something to do with this...... Nahh.... I don't subscribe to the 'screens straightening out the air' theory on these Bosch MAF Sensors.... hmmmm.....

Laterzzz
Matt

 

Matt, if you think about the forumla for HP, if you aren't making any more HP after 4,800 rpm (common for TPI), then you shouldn't be consuming any more air, which is what the MAF measures. I believe that you'd find a strong correlation to the MAF and a dyno.

As for the MAF Scalar Tables, I have noticed that there are a wide variety even among the other stock GM BINs for 1989. In the tests that I have done with other guys I know that have MAF cars, the ARAP BIN still seems to have the best MAF Scalar Tables (i.e. closest to 128/128). Some guys are copying the MAF Scalar Tables from the ARAP even if they are using a different BIN as a base.

This is what I have done recently for one friend that had a basically stock 88 305 Auto with good results.