I am close to putting my new engine in my 88 corvette (manual)(165 & $32B). The new setup consists of 383 @ 10.1:1 c/r, superram base and plenum, LPE(Accel) 219 cam,hooker headers, ford 30# injectors, 1.6 roller rockers, and AFR190 heads.

I have burned a few chips successfully and I am ready to burn my 1st one for my new setup. I am modifying my stock bin.

By my calcs, I *SHOULD* be running around 35# injectors, so if I bump my fuel pressure up to 54psi, I should be there. I need to then change the injector constant to 35. It is a MAF system, so I should be relatively ok? With the higher c/r, should I take out some of the timing?

I know I am going to have to do a lot of tuning once I get it running, but I'd want it to be able to start right up and then run for 15-20 mins @ 2500 rpms per my engine builder's break in recommendations.
Any other tips?

Bonus Qs that are not important yet but will be...When I start tuning am I better off switching to the $6E and ARAP code even though I may lose some of my digital dash toys? Or should I switch to the SD 730? Or stick w/ what I have?


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88 Z51 4+3 Corvette
94 Trans Am GT

 

8x35=280 or 560 HP at 100% DC
You just might run out of PW to get a decent idle.
You'll be pegging the MAF wayy tooo early to be useful in tuning.
The 730 is you only real option, and you might have to forgo that for an aftermarket one and peak and hold to get a decent idle

You might revisit my final amswer postings, in one I talked about injectors ecms, and there limits

 

I am running a 33lb injector constant in my 730 with my 350 and SVO 30lb injectors. Pulse Widths are around 1.9ms and the VE is way low because of the huge cam. It idles beautifully, albeit with a nice phat / fat lope. Should be able to pump the injectors up to the 36lb SVOs (with a 40lb constant) at 45psi and still idle ok.

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

You should talk to TODD85. He has a combo very similar to yours. His chip was done by TPIs. He runs mid 11's all motor. This is with a the stock 85 MAF computer (reprogramed). Apparently TPIs has cracked this goddamn 255g/sec limit. I wonder if there is a way to weasel the secret out of them. I hear that their files can not be read by our editors. Does anyone know how to write thier own def files? I emailed the ECM guy about this here is what he said...

I do not know of anyone that has found a way to go
beyond the 255 gm/sec limit.

This limitation is a software limit impose because the
code uses a single 8 bit value that is unscaled to
represent airflow (255 is the largest value that can
be represented with an 8 bot number).

If you were ambitious, you should be able to modify
the software (algorythm not calibration values) to add
a scalar to the airflow value or you could change the
value to a 16 bit value like the later LT1's but
algorythm modifications can be tricky.

and from another email...

The MAF reading is software limited to 255 so if the
MAF sensor puts out a frequency that's higher than the
stock equivalent of 255 gm/sec, the ECM just uses the
max air flow (255 gm/sec) for its calculations.

Can anyone use this to crack this damn thing? I think if anyone cracks this it will be to some like dicovering the fountain of youth or Atlantis.

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82' Z-28. 327" w/ flat tops. 216/228/112LS. Pocket ported 041 heads 1.94/1.50 SS valves. World Class T-5 from a 91'. Best run? Runs with 2001 vette to 150mph! Soon to be converted over to TPI w/ supercharger.

 

TPIS didn't crack the 255 limit. They just set PE engagement really low and use the PE AFR vs. RPM table to compensate. They are doing the same thing that other MAF tuners here are doing.

I still say their chips are junk.

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

I agree with Tim. In fact, that solution mentioned by Tim is what most tuners do when a Power Adder (ie. supercharger) is added, they just add more fuel @ PE. I did the very same thing as a "quick fix" for a guy that had a supercharger and did not want to change his 7730 ecm to 749 (SyTy) that can read a 2 bar MAP.

I've looked inside the code for the 165 and it is VERY TIGHT with very little room for additional code or tables. I initially thought the same thing...just change all the the table values to 16 bit from 8 bit, but I quickly ran out of room. And then, you have a problem with the basic 8 bit ecm in that it has limited 16 bit arithmetic functions. It is very easy to overflow the accumulators in 16 bit arithmetic if your resulting calculation requires a 32 bit result accumulator. This is what ECM guy meant about the actual algorithym (the actual code) can get tricky...overflowing the accumulator when doing 16 bit arithmetic.

 

Ok, last night I spent 4 hours pouring through the archives here and searching the gmecm. My brain is overloaded, so let me ask some more specific questions:
1)To just start the engine and run it at 2500 rpms, do you think an injector constant of 35 with a fuel pressure of 54 will run reasonable?
2) Do I need to take out timing or do anything else?
3)Am I understanding the following correctly?
When the engine has gone through the initial break in and I am ready to start tuning, the 255 gm/sec limit is gonna cause me probs because with the size of my engine and decent air flow, I am gonna hit the limit too low in the rpm band and have to fudge the fuel above that because the comp will have no clue how much air is really coming in. Therefore, I am better off with the 730 because I ditch both the air flow restriction and the measuring restriction, however I may still have a prob. If my stock engine had 250hp and I want 450, then with a gm ecu I really need to use 40# injectors(22#*450hp/250hp=39.6#) At 40#, my injector pulse width may be too narrow at idle. So as long as I am swaping I might want to go to an aftermarket ECU in which case my 30# injectors at a higher pressure may be fine. Any guess as to where I may hit the too short pulse width prob?
4)What are "peak and hold" injectors? Special injectors, or special way aftermarket ECUs handle injectors?

 

I think that will be way too rich. Put the fuel pressure down to 45PSI. Personally, I would use a FP of 45psi and a constant of 33lb/hr

Depends on what the engine wants. Depends on the current BIN. Depends on your modifications. Depends on what part of the tuning we are talking about. More specificity needed here.

Exactly.

I believe the SVO 36lb/hr injectors (which are equivalent to GM 39.xlb/hr injectors will be just fine for idle. Again, I am running 30's with a 33 injector constant and still have breathing room.

Guess? Heh heh ... in that case - sure. My guess would be somewhere after 40lb/hr depending on the modifications to the motor and the size of the motor.

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Tim: As far as timing, I am just talking about start up and break in. Since the above listed mods will have a higher compression ratio than the stock engine and bin, I thought I might need to be safe and retard the timing a bit. I dont want to be trying to do the initial break in and have detonation probs. I know that after that I have a LOT of tuning to do. I am jhust trying to get a good basis for the initial start and breakin.

 

Ok, great, now I'm not the only one to ask this! I assume the answer is something like "go through the archives!!" but I had to ask anyway

 

What is PE? What does the PE AFR vs RPM do? I have the same situation, I will be installing a S/C on a 165. I can not afford to switch, after purchacing the S/C. Sorry for my ignorance, but have little experience with this stuff (trying to learn.

------------------
82' Z-28. 327" w/ flat tops. 216/228/112LS. Pocket ported 041 heads 1.94/1.50 SS valves. World Class T-5 from a 91'. Best run? Runs with 2001 vette to 150mph! Soon to be converted over to TPI w/ supercharger.

 

PE is Power Enrichment. It is what most people think of when they say WOT. In reality, you can adjust the %TPS that PE is invoked. And you don't need 100% TPS to invoke PE, you just adjust it to when you want PE to kick in.

For my VE table chages, I set my PE value to 100% to keep from going in to PE. Once I am happy with my VE Table, I set it back to 60-70% range (or whatever you prefer).

That is why guys who are trying to get 4.5+ Volts from their TPS @ WOT are wasting their time. You only have to change the PE RPM vs %TPS table to whatever you want it to be.

 

So when PE mode in induced, the computer ignores the MAF sensor?

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82' Z-28. 327" w/ flat tops. 216/228/112LS. Pocket ported 041 heads 1.94/1.50 SS valves. World Class T-5 from a 91'. Best run? Runs with 2001 vette to 150mph! Soon to be converted over to TPI w/ supercharger.