Brendyn G

Hey guys so I have a 99 z28 with cam and basic bolt ons. It is a 4l80 car with a 3200 converter. All tuned by a reputable shop made 399 to the back tire. Going to the track, the car would only do 13.2 barely getting 102, car wasn't spinning but only getting a 1.9 60ft probably due to the small converter. But with the extremely low mph, I know something is wrong. So I am gonna do a log tonight to start. What are some things I should check, replace, or look into?

LSX Power Tuning

iTrader: (4)

Post a log and your tune, without those everyone would just be guessing. Do you have a wideband hooked up to show up in the log?

Brendyn G

Unfortunately I do not have a wideband hooked up. I attached a log and the tune

LSX Power Tuning

iTrader: (4)

Where are you located at? Are you higher up in elevation? Your map sensor seems off at WOT.

Brendyn G

Located in Ohio, its about 1100ft. Could I need a new MAF?

kingtal0n

iTrader: (1)

post dyno graph

If it was a dynojet I would expect a faster car

but if its any other dyno they can make it say whatever they want

Brendyn G

Mustang dyno... if this was any other shop I’d consider the possibly but this shop is extremely reputable ... owner is a great guy and they’ve built/tuned cars for many people I know .

Darth_V8r

iTrader: (4)

What rear gear?

Brendyn G

3:23. I thought of this too as this is trash but still thought it should be doing a little bit better . Maybe I’m wrong though

Darth_V8r

iTrader: (4)

it'll be hard to launch much better without gear. Something else -- your dyno curve was still going up, so I'm wondering --what is your shift point? you might simply need to raise your shift points. If you're peaking at 6300, you should be shifting around 6800.

Brendyn G

Not even sure if it’s that high. Will definitely check that out was actually thinking the same thing. Are stock ls1s with springs and push rods are good to rev to 6800?

Darth_V8r

iTrader: (4)

If your question is - can the bottom end take it? - the answer is yes. If you are saying stock springs and pushrods, I would go to 5/16 pushrods and psi1511 springs. The stock rockers are fine.

I wasn't sure on the phrasing which way you meant it.

Brendyn G

Sorry for the confusion, I put the springs and push rods in the car that came with my Texas speed cam kit, so they are not stock .

Darth_V8r

iTrader: (4)

Good! Then here is my thoughts. I think on your dyno curve, the operator did not rev it out far enough. I think your actual result if was fully revved out would be in the 405 range at 6300 RPM. And you're at 370 lbs of torque at 5000 RPM, which is about right. So the motor is working perfectly fine.

If there is anything in your tune, it would be raising the transmission shift points. if it's a manual, I would go with 6800. The bottom end can do that just fine. I have little direct experience with an auto, and have only built one hotrod with an auto, but you definitely need to be shifting at least 6500 just to get past peak power.

Hardware-wise, you do not mention converter. A 3600 stall converter will wake the car up if not already done. Coupled with 3.73 gears, your car will come to life.

Bottom line, i do not think the motor is the issue. Just have to work on the rest of the car some.

Brendyn G

Awesome, thank you for the good info. I’m gonna mess with the shift points this weekend for sure . Also the car has a 3200 converter . A bit small but I’m not huge into racing just want a number to make sure it’s all working good .

jlangley

iTrader: (8)

There must be something going on here. The dyno numbers and trap speed don't seem to match. My 01 SS ran 13.6 @ 102 bone stock. With current mods it did 12.6 @ 108. OP's should be trapping significantly higher.

What converter is it?

Brendyn G

I agree . It’s a summit branded 3200 believe it’s made by Hughes ? The car still runs good also, was pretty even with a 2019 coyote last night on the highway from 60. The track is slightly uphill that I ran at, might take a few mph off but not a ton.

jlangley

iTrader: (8)

You're about 100 hp more than stock at the wheels. That should get you around 10 mph trap speed imo. I'm no expert but I suspect the converter is the problem.

Brendyn G

i could definitely see this. I’m thinking it’s not a real “problem” as it is just a bad setup considering the converter is brand new.

LSX Power Tuning

iTrader: (4)

Need to check air fuel while at the track...also need to check converter slip....one of those will probably explain the low mph.