bjankuski

The results posted are from my 1986 Vette but the information gathered will also benifit the L-98 thirdgen's.

I have a 1986 Vette that is now powered with a 355 an automatic transmission and 3.07 gears, when the car was all stock it made 195 RWHP and 283 RWTQ and ran 14.25 in the quarter at 98 MPH. Last week on a 90 degree day with a moderate head wind I ran 12.83 at 105.7 MPH.
The mods done to the new power train are SLP cold air kit, AFPR, underdive pullies, descreened MAS, 52MM throttle body, Ported plenium, TPIS large tube runners, TPIS Big mouth base, 23 degree Trick flow 195 CC runner heads, ZZ-9 cam, 10.2 compression, TPIS long tube headers, Stock fuel injectors, and no precats or cat but stock mufflers. With these mods on the same dyno that I tested with for the stock runs I now pulled 286 RWHP at 5100 RPM and 352 RWTQ at 3300 RPM.

Now for the interesting part, about fuel pressure and Mass air flow sensors (MAS), and fuel pumps. On my first pull I was using a MAS with no screens but is still had the heat sinks in it. With the fuel pressure set at 42 PSI I pulled 282 RWHP at 5100 RPM and ran very rich with an air fuel mixture of 12 to 1 at 3000 RPM and then it declined to 11.5 to 1 by 6000 RPM. I then swapped in my descreened and heat sink removed MAS and changed nothing else. On this pull the car lost 7 HP and ran very lean with a steady (but lean) 14.5 to 1 ratio from 3000 RPM to 6000 RPM. On the next pull I increased the fuel pressure to 52 PSI and changed nothing else, the car then responded with the 286 RWHP pull (that was my best) but still ran lean at air fuel mixture of a steady 13.6 to 1 from 3000 RPM to 6000 RPM. During the run I watched my fuel pressure drop from 52 PSI down to 46 PSI at 5000 RPM. I quit testing after this pull because I need a larger fuel pump, chip tuning, or both if I am going to see any more improvements. The dyno operator believes there is at least another 10 RWHP in my combination if I can get my air fuel ratio to 12.8 to 1.

my conclusions are:
1. My stock fuel pump is not able to supply enough fuel pressure for my engine at 52 PSI (I do have a new filter) maybe with chip tuning and 42 PSI it might be able to supply enough volume, but I doubt it. (The engine HP for my best run is a estimated 357 HP at 5100 RPM and the torque is 440 FTLBS at 3300 RPM figuring in the 20% drive train loss for the auto.)

2.The gutted MAS substantially leans out the air fuel ratio over the descreened but not gutted MAS.

3. The stock tachometer is way off on my car. With each pull I lifted when my stock tack read 5500 RPM but the dyno tach was reading between 6200 and 6300 RPM on pulls. (Luckly I lifted at 5500 RPM instead of 6000 RPM). After studying the data I believe the dyno tach is correct my tack is wrong.

I am trying to get a feel for these power numbers, do they seem ok for the mods on a L-98?

L98IROCZ89

very interesting....

'87FAKE-IROC-Z

Like you said, there is still tuning to do, so I'd say those are good numbers to build on. I bet there is alot more in there.

Grim Reaper

Now you know why guys will burn their own eproms...there is ONLY so much you can do with "mechanical tricks". Eventually, you must get inside the eprom and "fine tune" there. You can also start controlling your spark advance too - which has even greater potential to increasing power.

I have found that there is a "very narrow window" on the spark advance. 2* too much, and you are either detonating or having a too of spark advance pulled by the Knock Sensor. 2* too little, and you are loosing power.

As for your MAF sensor, if you make changes (screens or gutting), you almost always have to "recalibrate" the MAF Scalar Tables.