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

[Brad Roberts]

Whoa.. Erik!

That tranny is a REALLY old version. They stopped using the exposed "Monkey motion" in the early 70's!! You could bump an open wheeled racer from behind using this linkage and knock the car out of gear..LOL They went to the enclosed linkage!

Great shots. I recall seeing them now (IMG:style_emoticons/default/smile.gif)

I like how you suspended the engine in the chassis. Like a Pro Stock drag car "motor plates"

B

[Thorshammer]

The trans is circa 1972. Whe the aircooled SV's were introduced. and yes you could bump a SV out of gear from the rear, however only in 5th and 3rd.

Many people said this wasn't going to work, and was'nt strong enough. i don't even have MK 5 gears. Primarily because I did not have enough cash to buy Mk 5 gears. The mk 9 stuff worked fine for me. Your breakage may vary.

One side note, I clutch all upshifts and all down shifts. and try to limit the shock on the trans during downshifts by matching the rpm as best I can.

Erik

[Brad Roberts]

I clutch all upshifts and all down shifts.

Can you explain this to the home user?

I gather from what you said:

Full throttle upshift but clutch in for upshift and downshift.

If Erik wanted to change the actual gears every 5-6 races in the tranny he could feasibly perform full throttle clutchless upshifts (and downshifts) This option gets expensive quickly.

I would imagine he is "stabbing" the clutch or just touching it during the full throttle upshift.

I have a question for Erik:

What about an iginition interupt for the upshift?



B

[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

[edgetoo]

I have been using Hewland/Webster transmissions for 34 years. (We shouldn't be
trying to convince you folks to go this route, they really work well!!!) (Your E & F
prod compeditors have been using Dog Clutch non syncro boxes for years.)

They are slide on, interchangable, Dog engagement, straight cut gears housed in
a modified VW type 1 case. (Webster is an American copy of the English box.)
The MK 5, MK 8, & MK 9 are made in 4 & 5 speed and will bolt to VW type 4 with
VW type 4 flywheel. (Slightly longer axles are needed)

Air Cooled FSV, & F-Mazda configurations have the shift on the right side. (While
the exposed rear shifter of the ACFSV could be "bumped" into neutral, a small
shifter bumper will prevent this.)

Water Cooled FSV, FF, F2000, S2000, and Sports racer configurations have the
shift lever on the left side. (These may have had the starter flange removed.)("Rino" VW type 1 cases are inexpensive and are stronger.) (Some sideplate
appendages may need to be removed to clear some starters)

If you wish more details, let me know.

Ed Givler

[Brad Roberts]

Ed,

I like the idea of running the Rhino tranny case with the Hewland/MK setup. Great idea!

Do you run a 914 with a dog box??


B

[edgetoo]

yep!

Ran a AC FSV for almost 30 yr before going to an FP 914-4 (FSV with fenders!). Have had the Hewland and Blake's motor in it for 2 yrs. (It now shifts like a race
car!)

Ed

[groot]

Just an update on my 915 BS.... I got a refund from the dude who sold it to me and I'm going to ship it back to him.

In the mean time, I'm going to run a 901 until I move to a Hewland.