Going with the 915 trans, I'm taking the plunge Options

[groot]

I've researched it and decided to go for the 915 trans.

Due to job insecurity, I'm not comfortable buying a Hewland at this time. And since I'd need a replacement 901 case (or at least a ring and pinion-see "Pinion failure" thread) which would run me a few hundred bucks, I decided a few hundred more for the added strength of a 915 might be a good plan.

I scored an '84 Carrara 5-speed for <$1000. I will flip the ring myself and replace whatever else needs to be replaced over the next few weeks.

I have to decide whether I should add a cooler and pump or not....

For now, I will run the stock ratios. Check out this gear chart.... 2, 3 and 4 in the stock 915 box are remarkably close to what I was running in the 901 box. I only used 3, 4 and 5 with the 901. Knowing that Topeka has some very slow corners, I know I needed a lower 3rd (901), which 2nd in the 915 gets me. The purple box is an estimate from Jake about where the race engine will make good power.

As for the linkage... I've got a few ideas. I don't want to spend the $$$ for the WEVO setup, although it looks georgeous. If there's interest, I'll post progress pics.

[Thorshammer]

Actually I lift very slightly for every shift. It is a small lift, But I don't find the advantage in lap times shifting with my foot matted and the RPMS climbing like crazy. I just haven't seen the need. I know the flywheel effect will give the car a momentary push. I have looked at data systems on cars being shifted like this, and the shift time isn't really reduced. If it is, it is a very. very small decrease. I just don't think the component stress is worth the limited decrease in time between gears.

So let me recap, when nearing the shift point I stab the clutch and pull the handle, while I slightly lift my foot off the gas. Then I mat the gas pedal as the the clutch is already released. It pretty quick, you can hear the shift on my race videos. It's faster than anything else I have heard in a 914. Plus the rpm drops are calculated so that the engine is in the power all the time. I think that is a really big advantage against the Limited prep crowd. If you can gear it and keep it in the power more than the other huy you have an advantage. This is 50% of the reason I choose to do a Hewland.

Todd at TCE does alot of formula mazda transmissions, He has a mk5 geared trans in a pikes peak hillclimb car that has 320hp or so, and he has put it in a special gearcase and it uses the mk 5 gears and he has no problems. This may be a answer for some of you. I don't think the FP/EP crowd has a problem. Ed Givler and I had HEwlands for the past two years with no issues. And MK 9's as well, no mark 5 gearsets.

Erik