97 GTP unexpected findings in tune

[animuL]

I got another 97 GTP recently. The previous owner had it for a few years and never did anything to it other than have the transmission replaced, he knew it had a cold air intake and cat back exhaust, but he wasn't a GTP enthusiast, just used it as a DD. After driving it the first time I noticed it felt much faster than my other DD GTP that went 14.0-14.2. So the first thing I do is check the pulley out, sure enough, its got a 3.4 pulley on it, the cai, the catback exhaust, but other than that it looks stock, still has the u-bend.

So I read the tune thats on it and notice for one thing, that the injector flow rate vs kPa is all set to 38.28 across the board. Thats nothing like my other stock GTP files. I went ahead and left it, just did the basic tunning items like neg torque management, and whatnot. I then took it out to log things and noticed that it was running 85% duty cycle on the injectors, and the MAF was showing 36lb/min of air, it was also peaking at nearly 11 psi of boost yet was running stock high octane tables with minimal KR. The LTFTs never got worse than 1% and STFTS were within 5-7%, O2s were pretty solid 910-920 mV at WOT.

Something just doesn't seem quite right here. Its not that modded, 3.4 pulley, cai, and cat back yet the numbers indicate that its making over 300 horsepower?? As I am typing this out it almost seems possible if it has smaller injectors than stock, yet has been tuned around them. Does something seem strange to anyone else?

[Perforator]

What numbers indicate it's making over 300 horsepower?

[animuL]

What numbers indicate it's making over 300 horsepower?

I'm not saying it makes that much power really, but thats the values its seeing and they seem way too high for the few mods it has. Does anyone else with a 3.4 pulley see 36lbs per minute of airflow?? Maybe the numbers are normal, I've just never ran a 3.4 pulley before.

[Perforator]

How do you figure 36lbs per minute == 300 horsepower? I've never heard that before.

I don't know about the numbers, I'm running a 2.8 and would have to check some of my older scans at home. The thing is though that the maf flow numbers are only as accurate as your ifr table. If your ifr table is incorrect, your maf flow numbers will be too.

[animuL]

How do you figure 36lbs per minute == 300 horsepower? I've never heard that before.

I don't know about the numbers, I'm running a 2.8 and would have to check some of my older scans at home. The thing is though that the maf flow numbers are only as accurate as your ifr table. If your ifr table is incorrect, your maf flow numbers will be too.

I don't mean to say its making 300 horsepower because the engine VE is probably 80% or less. I just mean that the MAF is flowing enough air to support that kinda power if the engine was up to par. I'm just trying to see if the numbers I got are consistant with what other people on here have seen. If they are not, then I know I need to look into it some more and see if the MAF table has been altered, but if they are typical values for a 3.4 pulley at 5900 RPMs then everything is fine. Except that still wouldn't explain why it has the injectors programmed in as 38# all across the board. The only reason why I don't just start over with a stock tune is cause the fuel trims and O2s look better than anything I've ever seen.

A few days ago I logged my other GTP that has a 3.8 pulley on it, it flowed 28 lbs per minute of air at 5900 rpms. That would lead me to believe a 3.4 pulley would have flowed about 31 lbs per minute of air, not 36 like the log file shows on the new car. So thats why I got on here to see what other people with 3.4 pulleys show for airflow rates.

[Perforator]

eh, i wouldn't put to much into the maf l/b hour number. If your injector table is wrong your maf table is wrong and you don't have a wideband so you could be commanding 12:1 but actually fueling with your maf table 10:1.

[starks]

possible it has a cam in it? you could pull the front valve cover. dont know how hard it would be to check the lift though

you could even see if it had stock springs by pulling the oil cap...although i run stock springs on my VS cam.

perhaps it was modded more, and the previous owner demoded it..but a cam is pretty labor intensive to remove....almost seems like it was powrtuner or hptuned at one point.

[bilemke]

That maf reading is not impossible. But, like said above, it could be skewed.. Did you compare the calibration against a stock copy of the same calibration?

And yes, 97 GTP calibrations have a flat IFR table (well, they do stock anyway).

[animuL]

And yes, 97 GTP calibrations have a flat IFR table (well, they do stock anyway).

Cool, thanks for that... I haven't checked in to this much more but did notice the injectors are stock. I'll have to compare the MAF table to a stock one and maybe hook up my wideband.

[JerryH]

If the car has a non-stock tune, I can tell you that the MAF table is not going to be stock. If it is stock... with a catback, CAI and 3.4 on it, it will need to be modded for best performance anyways.