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glyn
Joined: 16 Jul 2003
Posts: 8
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 Posted: Wed Jul 16, 2003 1:32 pm Post subject: building a 924 carrera gt to race |
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 Im building a 1980 carrera gt to use in events in australia such as targa tasmania etc.I need help and advice in the following areas,
1 Is there a source of different gear ratios for the porsche gear box,either after market or a porsche range.Who do i contact to source them
2 Internal engine mods are totally free for these events but I must use the original head and block.Can anyone advise on sources of stroker kits heads cams pistons etc to help lift the power output,every little bit counts.
3 The turbo and waste gate are free but the rest of the k jetronic system must remain standard.Can anyone advise how to get sufficient fuel into the engine under these rules to get good power out of it.
regards
glyn |
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-nick
Joined: 16 Nov 2002
Posts: 2699
Location: Cambridge, MA
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| Posted: Fri Jul 18, 2003 3:03 am Post subject: |
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1- i don't know where you would go in AU, but the folks at powerhausII (http://phii.net) here in the states will be able to tell you if anything is even available. one thing for sure is that the optional limited slip diff for the '79 and '80 turbo's is from a 930 -you'll want one of these 
2- a cam won't likely get you anywhere on a turbo
-pistons can be made by JE through http://ebsracing.com -also in the states
-stroking/headwork/etc. -i'd start talking to machine shops with flowbenches
3- the turbo's seem pretty robust, and the wastegate is from the 930. i think you'll be alright keeping those stock- just rebuild them.
-playing with the boost and trying to keep the wastegate shut until the last possible moment are things to work on.
-the k-jet is good for at least 220-240hp, i don't know above that. are you allowed the use of a 5th injector for enrichment under boost? i think dyno (aka rolling road) tuning using an air/fuel meter will show you if you're going lean or maxing out the stock system. Porsche used a 928 fuel distributor to get more fuel to their 924GT racecars, this justs doubles the amount of possible fuel through the injectors (need higher flowing injectors too).
sounds fun, keep us posted
-nick |
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Joes924Racer
Joined: 03 Nov 2002
Posts: 11964
Location: Oregon, Denver Colorado native!
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| Posted: Fri Jul 18, 2003 3:10 am Post subject: |
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Hmmm where would the injectors come from. why dont you use the whole efi setup. theres 8 you could have 2 to each hole.
_________________
1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo. |
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leadfoot
Joined: 11 Dec 2002
Posts: 2222
Location: gOLD cOAST Australia
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| Posted: Sun Jul 20, 2003 12:12 pm Post subject: |
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you may as well use a standard 931 then... then you will already have the necessary black and head etc, you could then bore out the block and put lower compression pistons in... get a bigger turbo and intercooler and presto, you would have the figures of a gt anyway...!! mabye quicker by the time you finish, stroking will help and if you are changing the pistons anyway you could do this at the same time... are you in australia?? which state... if it's in victoria i can recommend some places.
what year did the gt come out though, i though the division split for targa is after '81 isn't the GT an '82 model??
leadfoot |
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Lizard
Joined: 03 Nov 2002
Posts: 9364
Location: Abbotsford BC. Canada
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| Posted: Mon Jul 21, 2003 2:29 am Post subject: |
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umm -nick you stated a cam wont do anything in a turbo car, this is incorrect (or they wouldn't put in in there ) but no if the cam has a higher lift it lets in more air and fuel, and then you get more power, so a cam will help
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3 928s, |
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924CarreraGTR
Joined: 01 Aug 2003
Posts: 14
Location: Regina, Sask.
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| Posted: Fri Aug 01, 2003 4:02 pm Post subject: Best Solution for HP in 924 |
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Okay this is the best solution for adding that extra HP in your 924 or 924 Turbo (like me). I chose www.imagineauto.com , you'll have to email them about this. They charged me under 10 000 US for an engine that puts out around 300 HP, this is good stuff.
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Tyler |
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924RACR
Joined: 29 Jul 2001
Posts: 9136
Location: Royal Oak, MI, USA
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| Posted: Fri Aug 01, 2003 9:59 pm Post subject: |
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I was hoping John H would reply to this - since he's in the area and experienced playing with the GT. Too bad... maybe he's busy...
Oh, BTW - shipping for a motor to Aus I'm willing to bet is somewhat of a drag...
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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john h
Joined: 06 Nov 2002
Posts: 827
Location: Wellington New Zealand
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| Posted: Wed Aug 06, 2003 11:17 am Post subject: |
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| 924RACR wrote: | I was hoping John H would reply to this - since he's in the area and experienced playing with the GT. Too bad... maybe he's busy...
Oh, BTW - shipping for a motor to Aus I'm willing to bet is somewhat of a drag... |
yeah been fairly busy recently of work relate dstuff so have'n t had time to comment - here's my two cents worth
As for power from a GT - personally I wouldn't bore or stroke it - but spend the money on getting everything else right.
First the K jetronic is good fro at least 260 and probably more. The injectors are the same as used on the GT and GTS and these pump out 210 and 245 respectively. I've had over 260 on my GT replica. You need to monitor the fuel pressure and also the mixture so it's useful to put a lamda probe in and ensure that it runs is in the normal to slightly rich area.
Next put on an intercooler if the rules allow for it put in where the 944 have theirs -if not put it on the top -use a Mazda rx 7 core and modify to suit. If using the Mazda core and end tanks use a rubber tube and hose clamp joints to the throttle body -the end tanks are not strong enough on the Mazda unit to allow for solid mounts and the on off boost will damage it. If it's solid mounted then the tanks can tear. I also use a water spray over the intercooler ,using a common garden misting irrigation nozzle and a Falcon windscreen washer pump. This keeps the charge air cool
Add an additional oil cooler -small 9 row should be sufficient for fast road and most track work (up to about an hour). Remove the cooling strip from between the bonnet (hood) and the firewall this allows hot air out of the engine bay. This could create a problem in that the air then comes into the cockpit and some scruntineers don't like it (mind you on one picked it up on my car and made me put it back).
Also try and get a genuine GT engine computer (real rare) these have different advances and retards than the normal 931 and helps develop a bit more power.
Waste gate take a line of the vent to the wastegate and then feed air from the manifold into the top of the waste gate through a regulator (and boost gauge) this allows for safer control of boost and also stops the waste gate creep - normal wastegates will start to open at about 5 psi and full open at 10 (for euro cars).
If you're pulling the motor apart try and get some GT piston(KS brand ) if not available then use either the Mahle or JE units the KS I've used in my car are slightly lighter than the Mahle and because of their forged construction, they also seem to take the boost better than other 924 turbo's I've run up to 1.2 bar and sometimes almost 1.4 bar. Currently I'm running 1.0 bar as the motor's old and tired. If you're driving the car hard then to keep it on song you should budget for replacing the valve springs on a regular basis as the get weak with constant high revs and the car goes off song real quick.
Exhaust I've found the standard GT system is pretty good the car develops good hp using it and I've played with a few variations and found the standard is the best for my needs.
There are a few more little tricks but these are just a try it a see.
Main thing is keep the oil and water cool if this is maintained then the little beast is reliable and can pump out some good horsepower.
If you can play with the suspension then you can gain quite a lot f time out this area and the brakes. Just by resetting my suspension to how I liked it not what the "experts" recommended I managed to gain 2 seconds a lap on one of our circuits here. For those of you familiar with Manfield in NZ I went from an average lap time of high 1.26's to low 1.24's in the space of 1 week with just a rest of suspension and no other changes.
Brake pads and tires also make a bit of difference not only the handling and stopping but in your own confidence. I use a carbon metallic pad ther are as good as standard pads when cold and even much better when hot also as good of better than most otheh race pads. Because they work good from cold I can make up a few places on the first lap because the brakes are better than those around me - it then means I have a further 5 laps to keep them at bay.
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Remember a Porsche is not just for Christmas,
if you take it to pieces slowly it can provide anguish all year long! |
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924RACR
Joined: 29 Jul 2001
Posts: 9136
Location: Royal Oak, MI, USA
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| Posted: Wed Aug 06, 2003 12:04 pm Post subject: |
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Excellent info John, thanks from all of us!
Now I gotta get some paint on that car and start tweaking it! LOL
_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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Peter_in_AU
Joined: 29 Jul 2001
Posts: 2745
Location: Sydney, Australia
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| Posted: Wed Aug 06, 2003 10:05 pm Post subject: |
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glyn, my 5c worth:
Targa events seem to be about two things; going around corners really really well and finishing (handling and reliability). No point building a firecracker for a 7 day event.
Concentrate on the suspension, weight and reliability. Do you have a set of rules for the Tassie Targa? What class would a 924 compete in? A non-turbo 924 might actually be a better class car than a GT replica (perhaps not as sexy tho) but I do remember from the old rally days that winning class A (near production) was better and cheaper than not finishing in class D (homoligation special) but not as much fun as class E (prototype).
Read what John H has to say, then read it again and again.
Study the mods Porsche did during their 924 racing program.
Update your profile so we know where you're from.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)
Learn to love your multimeter and may the search be with you |
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Vince Ponz
Joined: 02 Nov 2002
Posts: 3581
Location: Florida
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| Posted: Thu Aug 07, 2003 12:06 am Post subject: |
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Thanks for the info.
I have a question for you regarding the rocker panel on your car. I called the maker of my GT flares and he does not have rocker panels for a 924 with this conversion. He claims Porsche lost them. 944 fenders too.
I need to finish the car but need help here.
Thanks.
_________________
"Never let them see you sweat"
77.5 924 modified track car
79 931 Euro stock
88 924S SE
87 911 Targa stock |
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augidog
Joined: 03 Mar 2003
Posts: 1360
Location: New Jersey
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| Posted: Tue Sep 02, 2003 12:04 pm Post subject: |
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http://www.924board.org/viewtopic.php?t=8701
_________________
1978 924 95 mile daily driver.
Audi TB/POR174M/High Flow Cat/2.25" exhaust
I knew that positive thinking thing wouldn't work. |
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