Paxton Supercharger.

sport200 · May 7, 2015

Hey, guys it been a while.. I'm putting a Paxton supercharger on my 86GT. I know its a old school set up, but I like old school. it matches the era of the car. I've got a good idea on a tune set up , but if any one has any pointers I'm open. I've got 24lbs injectors, 190l in tank pump stock rails and lines. fuel FMU with a 24lb disk in it,(the FMU is the only thing I don't know about.... timing s set at 10degrees. fuel presser is 42 with line off. I have a one step colder plug in it. it is a 306 ci , dart head , 10:1 compression , long tube header, GT/40 upper and lower. 70mm pro m , crane cam 544/544 288/288. blower makes 6-8 psi. anything will help thanks guys.

TOOLOW91 · May 7, 2015

That's a lot of compression to play games with a 190lph pump 24s and a fmu . Personally that car needs 42s a 340 in tank pump , ditch the fmu and a real tune ESP with all that compression . And maybe a meth kit to keep the detonation down . @84Ttop what say you ?

Sent from my iPhone using my fingers while my auto correct makes me seem illiterate

MY 85 GT · May 7, 2015

I have an old school Paxton on my wifes 91 z28 350 TPI car had paradise wheels go over the blower and he upgraded the impeller for a few PSI more...what i would do is get yourself an Air fuel gauge and see where your at in Boost you might be rich or Lean that way you can play around with the FMU discs...or down the road get yourself a tune where they can get rid of the FMU totally....

sport200 · May 7, 2015

I don't like the FMU set up. I have a auto meter air fuel gauge in the car in podded with my fuel presser gauge. Funny I just got it back from paradise wheels. He went through the whole thing , I'm putting a oil cooler on it is my next step after the track run on Friday. it feels good on the street. thanks for the info.

MY 85 GT · May 7, 2015

Yes i bought the oil cooler for her car too...Also bought a snow performance Meth kit for added protection...i do have an FMU on hers but GMs stink for tuning...so i really dont know how to do it other then an FMU i know i can go bigger injectors but dont know anyone who can tune for that on her car so im limited...lol i just go off the Wide band to make sure its running rich/safe...

sport200 · May 7, 2015

I'm starting to worry a bit about the same thing. I've had 150 wet shot of NOS on this same set up. It loved it. but I'm learning more and more about nitrous and blowers. I guess theirs a big differences. it seems to be fat to me.. but it has a great chance to run out of fuel I guess.

MY 85 GT · May 7, 2015

I would go with a bigger fuel pump...get a tune and bigger injectors..thats me tho...

84Ttop · May 7, 2015

TOOLOW91 said:
That's a lot of compression to play games with a 190lph pump 24s and a fmu . Personally that car needs 42s a 340 in tank pump , ditch the fmu and a real time ESP with all that compression . And maybe a meth kit to keep the detonation down . @84Ttop what say you ?

Sent from my iPhone using my fingers while my auto correct makes me seem illiterate

I agree that the 190lph pump is not going to cut it... As recommended I would look towards a 340lph pump and 42lb injectors, all while ditching the FMU. As far as the compression goes, it's doable just narrows the tuning window a bit. I would be curious to see how much total timing you have in the motor as you won't get away with much before you start burning rings or melting ring lands. Keep in mind that the older ball drive units (I'm assuming that this is what we are talking about here) are not nearly as efficient as the newer centrifugals, the inlet temps will be notable higher and this is where you'll run into your biggest problems. Secondly, are you using a bypass valve? I would suggest it for sure if you currently don't have one installed. Is the autometer gauge a wide band or narrow band?

sport200 · May 7, 2015

Yes on the bypass valve. and not for sure on the wide or narrow band? total timing its set at 10 dergees with the plug out.

84Ttop · May 7, 2015

sport200 said:
Yes on the bypass valve. and not for sure on the wide or narrow band? total timing its set at 10 dergees with the plug out.

Does the afr gauge read on a scale from 10-15 or is it lean/stoich/rich?
With the spout connector out your base timing is at 10 degrees, this is not your total timing. Total timing is what the computer is allowing the car to see when under load, it uses the base timing you set with the spout out as part of the equation. Before you go trashing this motor I would strongly recommend having a chip burned for it or invest in a BTM, you will find that while the motor runs good on the stock timing values I can assure you that it won't run like that for long.

sport200 · May 7, 2015

lean/stoich/rich. It has a s93 computer in it out of a 93 cobra. I live in the Cincinnati area. I don't know if anyone in the area burns chips. ill look in to it thanks a ton.

Gearbanger 101 · May 7, 2015

That old ball driver charger would come anywhere close to the need for 42lb/hr injectors, or a 340lph pump.....but they can be installed regarless.

I guess I'm one of the few that doesn't see an issue with the 190lph pump or the 24lb/hr injectors/FMU combination.

The pump itself has show to handle over 570hp N/A.....Even with 6-8psi on tap (which is really pushing it with this blower), so he should be well within safe limits. The Allen guys used to run 6-7psi all day with FMU, stock injectors and a 190lph pump. The 9psi kits would upgrade the injectors (probably cheaper than having kit specific FMU recalibrated), but still stuck with the 190lph pump.

My old Cougar made 410hp/456lbs/ft tq at the flywheel with the 190lph pump until in the tank until the guys of this forum scared me into upgrading....but it never fell off at any point on the dyno.

As for the FMU....the only issue I have with using one, is that they can't really be fine tuned for accuracy. You can certainly get them ballpark (Vortech has many options for various injector sizes) but It'll never be as accurate as an ECU. So while you may have one set up to meet the max fuel delivery needs (read: safe levels), it may result in richer delivery in lower demand regions. Not to mention unable to compensate for elevation or temperature. The result....a fatter A/F ratio in order to keep things safe up to peak hp.

Nothing really wrong with that....simply not an "optimal" set up. Still an otherwise proven, low cost and most importantly safe alternative though.

sport200 · May 7, 2015

Thanks for that reply.. I'm gonna run this thing tomorrow night. I hope it stay's together , after reading these post it seems to me that u need tons of fuel. I always thought that their is No placement for displacement. meaning that it still a 306 ci motor. if it was a 502ci I could see all that fuel being used. I guess I'm living on the lean is mean phase.. lol. I'm running a 4:10 gear ratio. 5 spd . I always ran a 26x9 ET street. I'm gonna go with a 28x11.5 to help the top end. I"m hoping to see a super low 12 second et. 118mph . it ran 11:86 on a 150 nitrous shot.

84Ttop · May 7, 2015

sport200 said:
lean/stoich/rich. It has a s93 computer in it out of a 93 cobra. I live in the Cincinnati area. I don't know if anyone in the area burns chips. ill look in to it thanks a ton.

The gauge that you have is a narrow band and is more or less worthless, it will not provide you with any appreciable information.

Gearbanger 101 said:
That old ball driver charger would come anywhere close to the need for 42lb/hr injectors, or a 340lph pump.....but they can be installed regarless.

I guess I'm one of the few that doesn't see an issue with the 190lph pump or the 24lb/hr injectors/FMU combination.

The pump itself has show to handle over 570hp N/A.....Even with 6-8psi on tap (which is really pushing it with this blower), so he should be well within safe limits. The Allen guys used to run 6-7psi all day with FMU, stock injectors and a 190lph pump. The 9psi kits would upgrade the injectors (probably cheaper than having kit specific FMU recalibrated), but still stuck with the 190lph pump.

My old Cougar made 410hp/456lbs/ft tq at the flywheel with the 190lph pump until in the tank until the guys of this forum scared me into upgrading....but it never fell off at any point on the dyno.

As for the FMU....the only issue I have with using one, is that they can't really be fine tuned for accuracy. You can certainly get them ballpark (Vortech has many options for various injector sizes) but It'll never be as accurate as an ECU. So while you may have one set up to meet the max fuel delivery needs (read: safe levels), it may result in richer delivery in lower demand regions. Not to mention unable to compensate for elevation or temperature. The result....a fatter A/F ratio in order to keep things safe up to peak hp.

Nothing really wrong with that....simply not an "optimal" set up. Still an otherwise proven, low cost and most importantly safe alternative though.

You have made some very good points! I don't see the sense in skimping on the fuel system especially with the higher than stock compression. When comparing fuel pumps, typically reduce the advertized N/A capacity to half when talking about forced induction. The same applies to injector sizing while it's not quite that dramatic of a difference. Back in the day, (i hate saying that, i'm not THAT old...) the things we did to bandaid these setups would make some peoples heads spin, extra injectors on a hobbs switch, junk yard this and that to make it work... you name it. While we were able to get by and make things work, the ability to properly tune these cars has replaced every rig that we ever came up with in years past. Point being, have a chip burned for the car and you'll be in the best shape.

84Ttop · May 7, 2015

sport200 said:
Thanks for that reply.. I'm gonna run this thing tomorrow night. I hope it stay's together , after reading these post it seems to me that u need tons of fuel. I always thought that their is No placement for displacement. meaning that it still a 306 ci motor. if it was a 502ci I could see all that fuel being used. I guess I'm living on the lean is mean phase.. lol. I'm running a 4:10 gear ratio. 5 spd . I always ran a 26x9 ET street. I'm gonna go with a 28x11.5 to help the top end. I"m hoping to see a super low 12 second et. 118mph . it ran 11:86 on a 150 nitrous shot.

I feel like a broken record when I say this.. Have you tried drag radials? They are more stable and will run faster both ET and MPH when compared to any bias ply tire.

sport200 · May 7, 2015

Nope ET streets is all I ever ran. I've been tossing it around. whats the best to run?

84Ttop · May 7, 2015

sport200 said:
Nope ET streets is all I ever ran. I've been tossing it around. whats the best to run?

26" tire 275-50-15
28" tire 275-60-15
I prefer MickeyThompson personally, tried and true. I don't miss the top end wobble that the bias ply tires had one single bit, we've been using radials for just about 10 years now on everything we build

sport200 · May 7, 2015

Awesome... Is their a certain rubber temp or anything like a regular radial?

84Ttop · May 7, 2015

Typically a drag radial does not need much of a burn out, clean the tires off see a little bit of white smoke and you're good to go.

sport200 · May 7, 2015

wow that would be different. thanks

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