need some serious advice and info ?85

turbobooster

Active Member
hey guys i know this might be the wrong question for this group but no one in the transmission answere me lol my question is this can i drop a 5 speed in my 85 GN ? i mean id like to know what r the ups a d downs for this besides making the hole for a clutch can this be done if so what GM tranny fits our blocks? an ez swap any info or comment highly appreciated thanx
 
Do a search on this topic in the transmission section...It has been asked MANY times before...They were designed to make the power that they do behind an automatic tranny...
 
You are going to loose all (more then you would when using a automatic) your exhaust pressure when you put the clutch in and then your turbo has to spool up even more then if you had a automatic............from what I have read that is the problem with using a stick.

Nick
 
Can and has been done..........not too difficult of a swap.

As stated above our cars absolutely do not like a manual trans.

Does sound cool.............if there were better, or even equal performance I'm sure you'd see more of em.
 
well that is some very helpful feedback from u guys the swap does sound ez but im not to sure no more from whatur saying about having to spool up even more which i dont really know much about what do u mean by having to spool up even more wit an manual than an automatic?
 
The way I understand it is that when you put the clutch in to shift your engine speed is going to fall well below that of a automatic transmission shifting. So not as much exhaust pressure because of the low engine speed, so then you will not have the power there that a automatic will have..........boost levels will decrease while shifting more then if a automatic shifted it for you............clutch in and engine RPM's go down further then with a automatic. I think repeated myself a couple of times in that paragraph. LOL.

Lets say the automatic shifts at 5500 rpms and drops to 3000rpms in the start of the next gear..............compared to a stick.....you shift it at 5500rpms..........and the clutch causes the engine to rev at 2000rpms.......thus you just lost pressure for the turbo to feed off of.......THAT IS JUST AN EXAMPLE, BUT I THINK THAT IS THE LOGIC BEHIND IT ALL.........I wish some tranny guys would step in here and set us all straight.

Nick
 
You can't build boost from a dead stop with a stick. Every time you shift gears and let off the gas boost goes to 0 and has to build back up. The constant load from auto keeps the turbo spooled. Our motors have a somewhat narrow powerband and the auto helps this a lot. With a stick we would be posting more Supra-like timeslips lol 13.5@130mph.

GM did test a manual in a TTA and if I remember right it ran a full second slower through the 1/4 but gained like 5mph in top speed.
 
okay keeping all that in mind the part where u cant build boost at a dead stop wit stick makes sense but on the other part about changing gears and ur boost drops as u let of the gas cant that be fixed wit an external wastegate to keep constant boost through every gear ?
 
It would be the same as trying to build boost in neutral. No load on the engine and the turbo won't spool. Maybe 1psi or so but not enough to make any kind of difference. The wastegate won't have any affect on this. Even if you kept your foot in it while you shifted, the load goes away and therefore boost falls too.
 
wastegates only work if your car is intercooled when you have pressure, and even then, it is only used to relieve pressure at points when it is too high. If you have an intercooler, coodoes, but with a manual tranny, as you shift, your turbo does not spin between shifts, because there is minimal exhaust for at least .5 sec (depending on driver). In that half a sec, a turbo spinning @ 4700 RPMS and say 15 lbs of boost, could drop to 2200 rpms, and 1 or 2 lbs of boost. The exhaust output is greater with an automatic because some load is always on the transmission for more exhaust to be exerted. As for a manual, as soon as you depress the clutch, the load is lifted, and the motor is no longer under any load, so the exhaust is considerably minimized, as opposed to a motor under a load.

The best example I can give you is, have you ever seen a big ass truck with too heavy of a load traveling down hill? Smoke would be pluming out of that trucks' stacks because the motor and tranny are taking all the weight, however, the second he shifts gears, the smoke stops, wether it be for a second, or even a half second, the is little or no smoke...All boost is gone. Then the truck shifts back into it, and a second later, the smoke comes billowing out again...boost builds up again, but @ a considerably lower amount. Same goes for cars, just less weight, and usually no deisel black smoke...lol...But the auto trannies are the best option for our cars as proven by most TR racers.

John
 
I think you have wastegate mixed up with BOV. A BOV on an intercooled car will help a tiny bit but boost still goes to 0 on a shift. BTW, turbos spin closer to 80,000rpm. I have friends with DSMs with big turbos and it's annoying waiting a second after every shift for the turbo to come back on line.
 
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