Hey guys. New to the site but been around cars forever. This is my first Camaro however (been into building trucks for awhile) and I am new to trying to tune the TPI. This is what I have to start out with. 1991 Z28 with a 383 and a TCI trans and stall with a paxton Novi GSR. Engine is fully forged and should be able to handle just about whatever I can throw at it. I just purchased the car this weekend and the first thing i noticed was the cap and rotor looked original and the wires were all cracked and arching from the headers. Nothing a little replacement wont fix not a big deal. Some people just dont realize how important correct wire placement is. So all that stuff should be in this week then back to ironing out the rest. Oh and How is everyone running wires for headers with the air tubes? Thinking under the headers like original or just cut the dang tubes off since i have to replace header gaskets anyway.

Now that the history is out of the way. What else can I do as far as tuning? It has a MSD 6BTM that is wired in with an accell coil. Larger Injectors and again a paxton Supercharger. I have not yet pulled the computer to see if its stock or not. Couple other things I have noticed are the speedometer is about 20mph off and the tach dosent work. It stays pegged. Any Help would be greatly appreciated. Here is a pic of the new Toy.

 

Maybe the diff gears have been changed and the correct speedo gears to recalibrate the speedo were not installed?

Common problem on your year
https://www.thirdgen.org/forums/elec...meter-fix.html

 

I know that tranny was changed to a TCI but I thought the 91's had an electric spedometer that was calibrated by the ECM? Could be wrong on that. Probably thinking newer than I should be.

I was just reading the tachometer fix when you replied. Guess i should have started reading more. sorry.

 

Different rear gear ratio or bigger tires need to be compensated for in the programming of the ECM. Stock is 4007 pulses per mile from the vehicle speed sensor.

 

ok ive read the articles about the programmer and ecm flash and what not but it was a bit dated. Whats the latest and greatest way of setting this stuff? Is there a way to flash on the go now or anything plugin related? I really appreciate the help guys.

 

the speedo drive and driven gears can be changed to compensate for tire size and rear end ratio changes dakota digital sgi-5 or change the drive and or drive and driven gears in the output shat in the transmission.

http://www.transmissioncenter.net/sp...n_______va.htm

 

You will need to burn the changes into the ECMs Memcal EPROM. Or have someone do it. There is a formula in one of the threads here to figure out the PPM. You could run on a AutoProm from Moates.net but that requires some programming experience also and is not a good long term solution.

 

Wouldn't that only be for a mechanical drive speedo not a VSS setup? I may be wrong but thought they were all 4007 ppm VSS in 91.

 

I would need to get under the car to confirm but i think what tunedperformanc is trying to say is that the vss is still ran off a set of gears in the tailhousing like the older model tranny's. If thats the case just swap out the gears accordingly and viola all is well in the world of speedometers again. Would that be correct?

 

So I gather by this these cars still require the computer chip be un soldered and have a adapter added so you can burn eprom chips with some software and replace them as needed. I was kinda hoping someone came out with a new computer by now that was easier to update but i guess everyone concentrates on the new stuff huh.

 

That would be correct. The speedometer cars are getting harder to find for the 700r4 Tci does have a listing for them and you can still get some from gm/acdelco

 

I realize that the VSS is run by gears but the problem to me is guessing the gears to get the correct speed if tires and gears are changed. A simple change to code is way easier. I realize not everyone can do that but then again not everyone can change gears either.

 

Right the OBD2 can be programmed through the ASDL but not these older OBD1 cars.

 

Gear changes are no problem. Done bunches of them. now programming eproms that is a bit of a stretch. Weird considering i am a network admin for the military. programming has never been my strong suit though. Guess im gonna have to learn a little anyway.

 

You might check the stickies in the Transmission and Drivetrain forum.

JamesC

 

Just did. Thanks. there some good info in there on swapping the gear sets out.

 

Don't let it scare you off. It really is something most anyone is capable of With the programs like tunerPro, you don't even need programming skills to change the VSS ppm.

Knowing that the gears can be hard to find and can take up most of a day to change, whereas the programming is less than a five minute job, I still think
that's the way to go at least on your car. But it is your car and only you can decide that. Good Luck.

 

What are the out come of the bit changes in 8d for the divisor to the 4k optical output ? Is there a formula based off the 1:1 4kppm expected input too the buffered output ?

 

Yeah what he said!! LOL I have no idea what he just asked just figured id chime in.

 

Monte, if you go the Programming route, this is a formula that I used to calibrate for a Tremec 5 speed with a ford 17 pulse VSS and 3:90 gears and it came out very close. In my case it was 51200 pulses per mile.

I found in the DIY PROM forum thread
VSS calibration for 8746 ECM after T56 swap

#Feet traveled per tire revolution = 26" * PI / 12" = 6.81' (measure your tire circumference and substitute for 26")

# tire revolutions per driveshaft rotation = 3.08
Feet traveled per driveshaft rotation = 6.81' / 3.08 = 2.21' (drive shaft if spinning faster than the wheel. )

# driveshaft rotations per mile = 5280/2.21 = 2389 (this should equal third gear(auto) 4th gear (manual) RPM at 60 MPH)


VSS pulses per mile = 791.2 rotations * 40 pulses per rotation = 31,650 pulses per mile (compared to 40,000)


There is some confusion on the pulses per rotation but read it though and you'll figure it out.

 

Im not sure what your trying to say compared to $8d definition but change on the vss is as followed for the vss pulse divisor.



B7 set = (10000000) value of 128... speedo reads 96 mph
B6 set = (01000000) value of 64... speedo reads 83 mph
B7,B6 set = (11000000) value of 192... speedo reads 73 mph
B5 set = (00100000) value of 32... speedo reads 65 mph
B7 , B5 set = (10100000) value of 160... speedo reads 58 mph
B6 , B5 set = (01100000) value of 96... speedo reads 53 mph

 

My reply to Monte 0185 had nothing to do with your post which could probably get answered in the DIY PROM forum. I'm not the guy for that. There are much smarter people there that can certainly answer your question. We were talking about whether to change gears on the VSS or do a prom change. We were not discussing editor stuff nor assembly language.

 

No big deal guys still learning so all is good!! I read most of the OBDII swap thread today and now my brain really hurts!!!

 

so you bring up the subject and know nothing about it Thats ok I did testing today to get my answers.

 

I know alot of the basics as far as wiring and building engines and swapping parts from newer to older is concerned. I can rewire a car from one end to the other with a wiring diagram and most older gm's without one. Went to school years ago and was a ASE master tech and gm mechanic but gave it up to work on computers when my kids were born for a more steady paycheck. Lazy a$$ ex didnt work so someone had to make some money to pay bills. Anyway what I dont get is what im looking at in the programs and all the binary language and what to change for what. Wish there was someone close by that could show me what im looking at then it would be alot simpler from there. But hey a little trial and error never hurt i guess. I got to reading th ODBII swap and man its pricey so what i think im gonna do for now is swap in all these part i just got today (major tune up stuff cause of PO.) and then have a new chip programmed by someone and drop it in. Maybe buy the aldl/usb connector and by a program and do some data logging to send to the chip guy. this is definatley gonna be a learning experience. thats for sure. Carbs are so much easier!! lol

 

carbs are much easier, But the speedo gears are the best fix and the next would be a sgi-5 from dakota digital.

 

Very cool. Just checked it out. I agree the gears would be the correct fix and any further adjustments could be fine tuned in the programming. Just want my 383 to reach its full potential. Im really hoping the PO was correct and the rear end is a 373 cause according to the rpo codes its oly a 273. which is really conna suck for playing with all the stangs around here.

 

You can easily find out what gears the rear end is. Its stamped on the axle. Im not too sure the exact location, but its inbetween the gear housing (center) and the wheel. If the Camaro was dd, it may be tough to read the code due to rust.

TunedPerformanc!!!! Whats up bro!! Havent talked to you in a while.

 

Unless they have been changed then i gotta pull the cover and look at whats stamped on the ring gear. Did I mention i hate Gear oil. LOL

 

hey andrew , the sgi-5 is looking better and better. jk Here is another neat calculator but you will need to figure out the information.

http://www.tciauto.com/tc/speedometer-gear-calculator

 

My electical buddy got me a resister and a pot yesterday so i should be able to fix up my tach this weekend according to the thread i read. Ought to be interesting. What is everyone using for spark plug wire hold downs if you run your wires under the headers? Think mine are gonna have to be run that way cause of the air tubes. May just pull the headers completely off and cut the air tubes off and weld the holes up though. depends on how much of a pain the rusty bolts are gonna be.

 

I'm running a set of livewires header wires I grabbed from Summit for $100 to solve the wire burning problem, I haven't had any issues with no loom, though it would look nicer. They're fiberglass insulated, w/ a 10mm core, all have heat shrink cylinder # labels at both ends, which great for doing all your plugs at once, and they reach my enormous HEI dist cap without putting stress on the ends.

Plus, they match the paint she's getting next time I pull the motor and tranny.

http://www.summitracing.com/parts/DUI-C9062PR/

These are for under header, they have 90* boots on all the plug ends. Comes in a red, black, yellow, and blue, too.

Hope this helps!

 

Hey I like That!!! Might try those next. Was looking at the moroso ones like that as well. I ended up just cutting off my air tubes and welding the holes up which helped alot. I kept the same E3.48 plugs since they were only about 1/16-1/8 of an inch longer that the accell shorty plugs i bought and had the right washer type style for my aluminum heads. I did however buy some of theose boot socks and used that on my number 5 as well just in case. Hopefully these will last till i get some better headers and all my electrical issues worked out.

Right now im working on my fans for the radiator. I grounded the green/white wire at the relay with a test light and the high side fan come on and the same for the grey wire on the low side so that tells me the relays are working and i have some bad sensors hopefully. Any more ideas would be greatly appreciated.

Oh and one more thing. whats everyone doing with aluminum heads and temperature sensors? I have some adaptors on mine that seem to be throwing the temps off on the gauge.

 

I was looking at the parts sites and noticed the ends of the coolant temp sensors are much smaller in diameter then the older ones. At least according to the pics anyway. I may have the older style sending unit for the gauge causing it to be off. Gonna buy all new temp sensors since my fans arent working right and just go from there. Do have a question though. WHat the heck are these for? They were just hangin behind my A/C compressor.

 

I'm running a derale fan controller to handle both of my fans with a 180 on / 170 off sensor in the 3/8 npt port on the front of my Weiand intake. I'm not familiar with the layout of the TPI manifold, so I don't know if it's got a port like that, but you can also get an adapter to splice it into your upper hose, or a sandwich adapter to put right under the thermostat housing if you choose to go the way I did. I recommend against getting a push through probe for the radiator to do this, I haven't known them to be very durable in the few times I've used them. Also, most fan controllers do have AC request overrides so your fans run all the time with the AC on.

Not sure about the coolant temp sending unit. I'm still running factory heads for the rest of this 305's life (read: until I find a 4 bolt JY 350 block.) Hopefully you'll have figured something out long before then, though.

 

Sorry, but I never brought up the subject. I was trying to help Monte out and you hijacked the thread on a different subject that belongs in DIY Prom IMAO. I'm sorry if you felt attacked or something. I'm also trying to help you on another subject in another thread and I hope that makes up for it.

 

Guys guys guys!!! Its all good!!! Now lets shake and be friends again!! LOL

I fiddled around with my cooling some and decided to hell with it and just cut the rigged power wire to my passenger fan. I started her up and let her run to see if the coolant temp sensor in the intake was doing its job. Well it was. Drivers fan kicked on and stayed on to cool it down. It appears that the coolant temp switch in my pass head is broken off which controls the pass fan hence the hardwire. So I jumpered the two signal wires together on the relays so I have a dual fan setup and backup in case one CTS goes bad the other one will kick both fans on when needed. After i replace the broken one anyway. Gonna replace the guage sensor this weekend to see if that gets my gauge somewhat closer. Next on to wiring all the NOS stuff up and making everything look presentable. Then onto computer tuning which I posted some queries in the power adder section. Think I might go with FAST XFI since they make a prewired harness and it easily tunable for my very novice skills. If i had someone closer that could help i might venture in another direction but think it will be easiest but certainly not the cheapest. lol.

 

Sounds like you have a good plan. Good Luck!

 

I didn't see a reply to your question so I'll answer:
Those are the A.I.R. solenoids still connected to the wiring harness.
You do not seem to have the A.I.R. pump below the A/C compressor or it does not have the output pipe with the diverter valve assembly where these used to reside. If you do not care to restore the original functionality, you can discard these.

 

Congratulations on your new toy and sorry to hear that your speedometer is off. It is neither easy nor cheap to correct.
As the guys already pointed out here, you have only two viable options:
1) replace drive and/or driven gear in transmission tailshaft (easy to figure out the right gear combination but not exactly easy to find the gears nowadays - and very messy)
2) install a Dakota Digital box (easy but darn expensive)

The option of reprogramming the '730 ECM are out the window, the ECM cannot compensate for tire/gear changes with programming. Too bad, it would be a great solution otherwise.

But there is another possible solution. If you are not in a big hurry, I am working on a small device that will allow frequency adjustments which will help exactly with your scenario (and I am in the same boat, btw, after an axle swap).

Let me know if you would be interested in being a guinea pig.

Lou

 

Always interested in being a guinea pig!! The speedometer dont really bother me that much. After all there is an app for that!!! LMAO!! I downloaded an app for my phone that has a HUD option. Pretty cool but there is a drawback. I need one of those good rubber covers to keep my phone on the dash!! LOL And thank you by the way for the answer to the air solenoids. I kinda figured thats what they were but all that was done away with long ago. In fact I finished it off by cutting the air tubes off the headers and welding up the holes. Made it so much easier to run spark plug wires. Oh and got my tach fixed last night. Soldered a 500k POT in place across joints 4 and 10 like the thread mentioned so now I can Adjust it if needed. Just gotta find a good spot under the dash to mount it. Upped my base timing to about 10 and man did it ever start coming alive now. Next thing im gonna need is some frame ties and lower control arm relocation brackets. Gonna have to stay out of it a bit till then to make sure i dont twist anything. Well thats all i can think of for now.

 

Glad to hear the good news about your tach. It really isn't a hard fix. Just takes precision work and a little bit of skills (I know, I know, hard to find nowadays in the general population ). You can use a 220K trimpot which is MUCH smaller and you can solder it directly to the tach driver board. Once it is set, button it all up and you don't need to touch it again or run any wires to the potentiometer. Just my $0.02.

For the speedometer adjustment, I ordered the parts earlier this week and am hoping that they will be here Monday or Tuesday. I really want to fix my speedometer which is about 25% off now after my axle swap. I will let you know as soon as I have the adapters ready. I am hoping by the end of next week.

 

Cool. I know mines right about 20mph fast. According to my phone app which uses GPS.

 

Figured I would post a couple pics of everything pretty much straightened out in the engine bay. Got my tach fixed and everything put together and been driving it a couple days now. Now on to the fun stuff!!

 

Monte, I got the speed adapter circuit all soldered up and tested but now I need to test it in the real world, i.e. on my car. Though that one is sitting on jackstands in the garage (afterall, it IS a Chevy ) needing a battery etc so it will take me a few days to get that straightened out (with my crutches, now newly screwed-up shoulder and other obstacles).
Once I know this one is good, I'll build more and you can have one of them to try in your car. Feel free to PM me when you'll be ready. Btw, do you have PayPal?

Regards
Lou