hi have a 91 z28 5.7tpi and im looking for anyones opinion about my car.
I just got back from the track and had PERFECT TRACTION and 75* air,
best time-
60'-1.8
1/8-8.5 @ 85mph
1/4-13.6 @ 95mph

my mods
full exhaust-shorty headers back, no cat or mufflers
full msd ignition
gutted air box W/ air foil and k&ns
FPR
upgraded injectors
3.73 gears
drag radials
2500 stall
TUNED- ebl f4 flash tuning computer
and some other smaller things

stock block, cam, heads and tpi intake

my question is, is my 1/4 time and mph seem off? I only picked up 10mph and ran a great 1/8th but only a 13.6 1/4. it seems to me that I should be a little faster than that.

(((I ran a 1/8th= 8.9 @ 76mph 1/4= 13.7 @ 98mph before my gears/stall/old computer with a chip/street tires/and stock exhaust w/ dumpoff.))) so after all that I gained only in my 60', and 1/8th mile? seems like I would see a much better 1/4 mile.

***I JUST BOUGHT A HSR MANIFOLD hoping to see the 1/4 mile gain I want.***

any and all inputs welcome!!!!

 

Does seem off. How did the back half of the track feel? Did car rev to high with the 3.73? Did it shift to od? Or did you over rev in drive, way out of tpi's powerband?

13.6 at 95 is pretty good for stock tpi with those mods. About the same as mine did except i was in cooler weather with 3.42's and trapped 97 on my 13.63 run.

85 in the 1/8 is as fast as my bolt on ls1! That seems high for an l98. 8.5 et however should definately equate to a quicker 1/4. To me i see that as an intake restriction and to much gear for stock tpi. Or else the trans is slipping or converter locked during the 2-3 transistion and lugged motor down. Try verifying converter is forced unlocked for the 1/4 mile run

Hsr will see noticeable gains! You will not be disappointed. Retune and play with shift points. They willl be higher than tpi shift points. Should run low 13's no doubt, but could use alittle more stall with hsr, 2800-3000

 

When I get home ill post the time slip. But the back half seemed to fall on its face. My AfR was was 12.8-13.4 the whole time. I left it in od and I can't remember if it shifted or not. But I do know it didn't over rev. And should I throw some 1.6 RRs in there since I'm wrenchen? Will it make a difference?

 

1.6's do help, especially with the hsr intake

 

I don't see where you are off, Exhaust and gears are not gonna gain you full seconds. I ran 9.1 8th miles bone stock this Friday. You are running 8.5 with no power adding, that's what I would expect. If you use an 8th mile converter, you should be running 13.4, and you are near that too.. I think you are getting exactly what you should be in my opinion..

 

Gaining 10 mph on back half is a clear sign something isnt right

Most na cars gain 20-23 mph. My ls1 trapped 85 mph 1/8 and hit 109-111 1/4

Car that doesnt have top end or has a top end issue will be below 20 mph gains. Unless his track is not accurate at the 1/8...

My L98 went 80 mph 1/8 and 100 mph 1/4 with stock tpi with bolt ons. Tpi is not a great top end intake but still should do more than 10 mph on big end

 

Me personally, I would run it with stock gears and keep the stall. I think you are stretching her out of her powerband a little bit. With that short gear 1st gear of the 700r4, I wonder if those gears aren't hurting your top end...

 

that's what im thinking. the 3.73s may be a little much. because at the 1/4 im at top of 3rd if not, then im in OD. it didn't sputter or anything the back half, it just didn't pull like 1/2 and first half of 3rd. so idk.
I did just pick up a HSR this morning, hoping it will help. but if I run out of gear in the 1/4 then whats the point.

 

do you guys think its possible at all to see a less than a 13.6sec pass with the set up that I have? maybe diff gears and play with the tune?

 

If you were running 13.7 before this, you should be pulling 13.3-0 I would think.. Are you running an Adjustable FPR? What Pressure?

 

If you have a data log of any of the runs you can check it to see when the trans shifted. Along with if/when the TCC locked up. Using the 1/4 graph in the analysis display makes it easy.

RBob.

 

13.6 on a stock tpi intake l98 with those mods is good. But that 1/8 mile shows it should be quicker.

1.8 60 foot aint bad but 1.7's possible. My 13.6 was on a 1.75

I had a friend run 3.70's in his firebird L98 with siamesed tpi runners and it fit the powerband well. 3.73 fits hsr well.
Stock tpi will fall off pretty hard after 4500-4600 rpm. You'd want to shift in that 4600-4800 range. Hsr or siamesed tpi will pull to 5200 before falling off like a rock. Shift 5200-5500.

More rpm range will fit the gearing

 

Well I started the tear down to put the hsr on. Then I'm going to look at my tune more closely now. My old tune may have been out of wack. I'm deff going to data log next time I hit the track, I'm hoping next week. please explain the TCC and when it should lock up. Iv always been confused about that.
BTW thanks for all the help!

 

I do have a afpr, I have a fuel pressure gauge and a Af/ratio gauge inside my car. I tuned it accordingly for my ratio. Right now its 50psi and 12.5-13.2ish across the board, give or take.

 

My cars always ran best with tcc disabled for the 1/4 mile. Factory bins usually set between 70-90 mph, i cant recall exactly but i usually force unlock prevention threshold to some way high value like 130 mph. Idk how ebl does it but you can play with it

 

The P4 Flash BINs have it set to 100 MPH:

TCC - Forced Lock

That is, once over that threshold the TCC is forced to lock.

Not pulling as well on the top of the track may be due to too much SA. While the SA is OK at the beginning of the track. If the transmission is shifting into OD, can pull a few degrees ( 2 - 2.5*) using this table:

SA - PE Retard in 3rd & 4th (auto only)

I don't know of any 3rd gens with a 3rd gear switch, but they all should have a 4th gear switch.

RBob.

{edit: to clarify my last statement, all those with the 700R4 should have the 4th gear switch. The '89 TTA with the 200-4R has both the 3rd & 4th gear switches.}

 

thanks! when I finish the stealth ram ill start from scratch with the tune and see where it takes me. ill keep posting updates!

 

RB0b-
SA - PE Retard in 3rd & 4th (auto only)....3rd & 4th are set at 0* across the board.(sound normal?)
TCC - Forced Lock.....is set at 100mph
anything else I can look at that may be out of wack?

 

Nothing out of whack with those values. That is what they are in the provided BINs/calibrations. Just need to find out if pulling some spark advance in 4th helps.

RBob.

 

Okay ill do that. I'm almost done with the HSR swap so ill have it out this weekend.
My base timing is set at 12*
Do you think that may be a bit high? Im thinkin of dropping it down to 8-10

 

Watch the AFR, it will likely be rich at peak torque, and lean above it.

You can set the base timing to any reasonable value. Just make sure that the "SA - Initial SA" in the BIN matches.

RBob.

 

thanks! the initial SA matches. That is exactly what my AFR does with the tpi set up. im curious to see how the stealth ram runs.

 

What is SA?

 

Spark Advance. The ECM has the distributor base setting in it's calibration. This is so the ECM can calculate the proper time to fire the spark plugs for the desired SA.

RBob.

 

Rbob-(or anyone else that knows the answer)
The HSR swap is almost done and I have no EGR and just want to make sure that it wont act up.
Is there anything I can change on my EBL tune to make sure I don't get a SES light due to deleting my EGR? is there any value I can change?

 

UPDATE**
I just found my other time slip from the same track day.
I ran
1/8- 8.7 @ 82.65 mph
1/4 13.7 @ 97.31mph
that's 2.5mph faster than my 2nd run- 13.6 @ 94.89!!!!! something had to be off on my second run.

I really wish I data logged for both runs!

 

For the EGR, set this value high:

EGR - CTS Enable Threshold

RBob.

 

The bin already had it set to 150.50, which is all the way up. this will this work fine with my car having no EGR?
and again thank a ton for the help!

 

Yes, it disables all EGR logic. We set the emissions and VATs disabled in the provided calibrations as many end up in engine swap and off-road vehicles. Saves a lot of support headaches.

RBob.