need some ideas on the circle track car

fresh built ln2 ... stage 1 cam from WebCams, crane 1.6 roller rockers, manley thick wall pushrods, very mild port work, 3cc's shaved off head, stock bore, but new rings,bearings etc... about 10.1:1 compression

95 odb1.5 chipped ecm ... egr shut off , mild spark advance, PE mode engages earlier (tune was done for stock motor before these mods)


when i blip the throttle from idle it doesn't have the throttle response i would have expected (or even the response the stock motor had)... it sounds like its starving for air if you know what i mean

once its reved up a bit throttle response seems normal

but from idle it cant get out of its own way

haven't driven it on the road as its not street legal and still breaking in the motor

as its obd1.5 i cant get live data from it but there is no CEL

is it a bad sensor or something ? or could it be the tune now that it has a bigger cam, headwork and more compression then stock ... do i need to increase the injector pulsewidth ... or where should i be going for tuning changes with theses mods?

any thoughts or ideas would be appreciated

I also have the 95 OBD 1.5 computer. There is a way to data log. I've done it on my with Tuner RT Pro, and their Autoprom cable, which plugs into the "fake" obd2 port under the steering wheel. But, anyways, I had something similar, and still do in the low end. I would guess it's just the need for the tune. Do you have a wideband? I've had one for years with my car in it's current configuration, and it has helped me to understand why it's running a certain way in moments. I.E. sometimes, if the idle gets really rough as I pull up to a light, I look at the wide band and see it's super lean, like 19.9, or 20.0, and it takes a moment for the computer to figure things out, (probably cause it's so far from the original cell's expected fuel) but once it figures out its lean, it gives it more fuel, and the idle smooths out, and the fuel ratio comes back down to 14.7

Try filling out your profile. It will help with questions in the future, but anyways, if you don't have a wideband, get one. You'll want it when you tune anyways. Other than that, I don't actually have much experience with the tuning of these 1.5 beasts. I want to learn more, but my time these days is spent elsewhere, and you really need to relocate the ECU to just under the passenger foot well if you really wanna tune and re-tune, since it requires running a ribbon cables from inside the ECU to your computer, and you don't want to leave it exposed to the elements like that (currently near the front right tire.)

i did figure this out a while back ...

it turned out to be one of the injectors was bad, found it when i went to do a compression test and one plug looked as it had never been fired, the injectors were a brand new set from our sponsor (a fuel injection company) so we kinda wrote off that possibility in initial diagnostics ... boy was i wrong lol

i still don't have a wideband as it would be illegal in our class of racing, but i bought a tiny voyo computer that has a battery and hide it under the dash when i datalog under racing conditions =)

the tune is fairly solid now and we have the car about a second behind the fastest guy on the track

the only issue is it lacks acceleration coming out of the corners ... so we just picked up a transmission out of an old century that has the 3.06 differential in it and will be swapping that in, this should up our final drive from the stock 3.18 to 3.43 and hopefully that will get us out of the corners and put the rpm range up where we want it

if all goes well with the diff swap i think we will find the second we need and have a super competitive little LN2 =)

Not sure if you're interested or not, but while you have the diff out, it may be a good time to replace/upgrade the spyder gears. but you'll need to do the research on what the century has in it. The factor trans on the LN2 was know to have issues (especially under launch conditions) or snapping the spyder gears, since they were cast powder and not machined metal. You can find machined ones from a 92 Isuzu transmission diff. But maybe the Century already has good machined spyder gears, since it was matted to a much more powerful engine to begin with. You could also throw in a a limited slip (the spring based one, since the real LSD is $1,000+) Like this: http://www.chevycavalierworld.com/phantomgrip-lsd.php

All kinda depends on your race conditions, and how you use/abuse the car, lol.

Oh, and out of curiosity, how did you end up tuning the car?

sorry VTloki

i just saw your response

as for tuning i ran a pc on board while racing and dataloged with Tuner Pro RT to fine tune the fuel and spark advance was just a trial and error ... kept bumping it up till we lost power and started seeing knock

other than that we killed egr and emissions, turned off the TCC lockup and made PE come in much faster with a very low delta tps