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The dark shall be with us
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Discussion Starter #1
I have been trying to figure out which gearing set up is going to get you the quickest acceleration and speed. I know a shorter gear ratio will give you a much better acceleration but on turbo cars, it seems its a disadvantage. How much of a disadvantage is what I can't figure out? I have seen STI lose to WRX because the guy has to keep shifting. I also have seen short gear ratio cars that are pretty fast for the power they make.
On this video at 37:00 min mark, you can see every time he shifts, The GTR jumps half a car.

but here, you can see this car keeps on accelerating after a shift at 3 min mark
I know both don't fall out of boost. So the question is does a manual car benefit from longer gear because it stays in boost without shifting or would shorter gear benefit the car more if it can be shift faster? but too short of gear and car Won't stay in boost long. This obviously doesn't apply to automatic cars since the torque converter is a torque multiplier itself.
On a 5 speed car,if we rev the engine to 9k or more rpm, we can get a lot of speed with just two shifts. this is what I came up with after extending the graph. On my car I have benefited from my 3rd gear shift beating cars with similar power. but I have been wondering If I go with shorter 3rd gear it would help me more or go with longer 2ng gear to avoid falling out of boost from 2nd to 3rd gear. The only other way is to rev the car to 9500-10k rpm in 2nd gear. That way engine can stay above 6k rpm.
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for example. Here I'm racing a tuned bmw 235I auto 8 speed. owner says it makes 450whp. My car makes 470whp and probably heavier too and yet I can beat him.
 

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Keep'n 'em spooled
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I'm only repeating what I've read/heard other experienced, respected members say:
1) yes, some prefer the 5 spd vs 6 spd for drag racing because they can wind out in 3rd gear vs having to shift to 4th with a 6 spd
2) guys making big power don't like the MR gears (higher ratios for all gears), say they feel like they have to shift too soon

You're talking about changing the ratio of a single gear (3rd) like its an easy option. Do you have any idea how much it would cost to get a pair of custom gears made, including heat treating, post heat treating finishing, etc.? Talk to the person that recently had some reverse gears made up to get an idea, and your quantities would be much lower which will increase your unit cost.

FYI I'm planning on installing MR gears on my (soon to be) DR-750 street car.
 

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The dark shall be with us
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Discussion Starter #3
I probably should have been more specific. The setup will be on a face plated or dog box transmission. I know it cost money but no point of build a car if it can't use the whole power or stays in power for long. I'm planning to do face plating first when my synchros go out and if that didn't hold, I'll go dog box.

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Diminishing returns are insane on transmission upgrades sometimes. There's a guy on youtube called Mazzei Formula with a 4 rotor rx7 and he has an air shifted sequential dogbox. That transmission setup probably costs 50k and it probably saves him 1-2 tenths of a second each shift. It makes sense for him because every single part on his car is at the highest level, but for us plebians investing 50k into an engine would give orders of magnitude better results.

It would be awesome to rev to 9k. With a 3% change in tire diameter you could hit 60 in 1st gear at 9000 rpm. That could get these cars down to sub 3 second 0-60 times with an aggressive launch. We'd be picking fights with p100ds easy. I don't know if there's good information on how to reliably rev to 9k though. Definitely need a completely built and balanced engine, massive turbos to make power up there, and maybe an oil tank and dry sump system for reliable oiling. I wish someone would make a good guide on how to do it reliably.
 

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I wish someone would make a good guide on how to do it reliably.
If you search around there are threads of people(specifically Ninja) getting to 9k on stock oil system components. I think the formula would just be a healthy engine with good tolerances, high pressure valve springs, and a safe way to tune that high such as AEM.
 

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1G Foglights b!tches
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Drag race or road race?
What's the rpm powerband of car?

If it's a straingauge shifter dogbox car, you would want to just keep it in the HP powerband as tightly as possible in a drag situation. If you have to clutch it or lift, then that might change the gearing dynamic.

Road race might be different since I imagine you won't want to shift up or down during a turn or sweeper but you should be planning ahead anyway and the strain gauge shifter ignition cut can be tuned to manage power during the shift and not upset the chassis.
 

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The dark shall be with us
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Discussion Starter #10
Drag race of course. For road race I think shorter gears are a way to go.

I have watched man 3s racing. The 2nd to 3rd gear is a killer. Not because 3rd is long but because you are out of power band for too long. I would love to find out how well the car would perform if reved to 9500 in 2nd gear and go to 3rd.
 

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One fix at a time
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Shorter gearing would be better if you have a dogbox, sequential shifter setup with a strain gage that is tied to a standalone for no-lift to shift fuel, timing, and boost settings as well as a setup that you don't have to push the clutch pedal for shifts. The name of the game is the quickest shifts with the shorter gears so you are always in powerband. You can see some struggle in Brian's single turbo Elite dogbox sequential setup as he falls out of powerband on 1 or 2 gears. It's all about how you set it up as far as reving and so forth to do whatever you can to keep it in the powerband. You're not going to be very competitive if you have to manually shift a manual if you want to keep up with the automatics.
 

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The dark shall be with us
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Discussion Starter #12 (Edited)
Shorter gearing would be better if you have a dogbox, sequential shifter setup with a strain gage that is tied to a standalone for no-lift to shift fuel, timing, and boost settings as well as a setup that you don't have to push the clutch pedal for shifts. The name of the game is the quickest shifts with the shorter gears so you are always in powerband. You can see some struggle in Brian's single turbo Elite dogbox sequential setup as he falls out of powerband on 1 or 2 gears. It's all about how you set it up as far as reving and so forth to do whatever you can to keep it in the powerband. You're not going to be very competitive if you have to manually shift a manual if you want to keep up with the automatics.
That's what I have been thinking but Brian actually did good in 2nd gear. He was out of boost in 3rd gear. He needs to rev higher or get a shorter 3rd gear. I wonder how well these sequential shifters do. It seems they don't shift as good and as fast as a real sequential transmission.
It seems you have to build the gearing based on the power you make. Apparently if you build the gearing in a way that puts you back in power band every time is the best set up. Doesn't matter what gearing you use.
but then again I was about to beat a 8 speed automatic car that makes only 20-30 whp less than me. So does less shifting matter? I would have assumed that BMW would at least keep up of not beat me when it has such short gearing and stays in the power band. Watching the video shows the car shifter 2-3 times when I only shifted once.

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The dark shall be with us
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Discussion Starter #13 (Edited)
I did some testing on Gran Turismo game. That's probably the best testing you can do without spending money on parts for testing. I think I'll go with longer 1st and 2nd gear. After some testing, it turned out that's the best performance you can get without causing much problem when drag racing. For roll racing, it's the best set up. Long first and 2nd gear and leave the 3rd and 4th as is. I want to get 200mph in 4th gear.

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The mr gearing looked awesome when matt ran them even though he felt they were to short. Dr750s and slicks and a new tc case the gears went. With 24.5 tires its similar to what some evos have and they do good in the 1/4.
 
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I did some testing on Gran Turismo game. That's probably the best testing you can do without spending money on parts for testing. I think I'll go with longer 1st and 2nd gear. After some testing, it turned out that's the best performance you can get without causing much problem when drag racing. For roll racing, it's the best set up. Long first and 2nd gear and leave the 3rd and 4th as is. I want to get 200mph in 4th gear.

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The SCE dogbox is setup that way.
 

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Is there a specific goal you have that you can't accomplish with more power?

In terms of drag racing, trapping above ~115 in a 6spd car sucks, that shift to 4th right before the finish line kills it! Did the 1/8 in 7.59 @ 92.8 to only run an 11.8 @ 116.
 

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I dont make enough power to have to shift to 4th yet. With the gear calc and looking at the evo 8/9 gearing, we lose a lot more speed/rpm going into second and like you say 4th just bogs unlees you have the power there. Thats even with 9k shift points. I guess there's no 'cheap' way around it, a custom elite dog box is the way to go to get the traps needed. What rpm did brian trap the 150 on stock gearing?
 

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The dark shall be with us
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Discussion Starter #18
Don't know about rpm. but you can figure it out by looking at the gear ratio chart. The tall gearing and not enough rpm is why we don't do well. in 5 speed, you drop to 4500 rpm every time shifting. the bigger the turbo, the worse it performs. .
 

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The dark shall be with us
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Discussion Starter #19
Is there a specific goal you have that you can't accomplish with more power?

In terms of drag racing, trapping above ~115 in a 6spd car sucks, that shift to 4th right before the finish line kills it! Did the 1/8 in 7.59 @ 92.8 to only run an 11.8 @ 116.
That's a pretty good time for 116 mph. I ran 11.7 at 120. 1.8 60 ft.
 
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