will the hewland handle a twin turbo?

[tmurph]

I've been toying with the idea of a rotary twin turbo (from a rx7) in my FM for our hillclimb events.

I haven't found any spec on the hewland and wonder if it might be too much?

[Brian]

If the Formula Mazda box is essentially similar to a MK9, then it is rated to 150 ft lbs of torque and 180 hp using M type gears. If an upgrade to M type MK 5 gears is possible, that goes up to around 180 ft lbs of torque and 240 hp.

BTW, I found this in three minutes with Google.

Brian

[Dave Cutchins]

Timm,

I think I may be on the edge with my 6-Port Renesis.

I don't know the numbers for a Twin Turbo but I found this:

http://www.hewland.com/svga/mk9.html

[pahillclimber]

Tim,

NO, Find out from either Moreck or John Finger, current owner of the Moreck Reynard, and find out what they used or have for a transaxle. Moreck's Reynard was a handful under power; especially, when the turbo kicked in. My thinking is that you would have to do more work to the chassis just to keep it on the road. Have you maxed out the porting and carbs yet? Would a 3 rotor work?

Rich Sweigart

[pahillclimber]

Tim,

John is using MK5 gears; which would require some machining to your gearbox in order to work. Let me know if, you are going to go this route; I have a hillclimb MK5 first and second that could sell you.

Rich

[Brian]

I'm now very curious - what manufacturer made the FM gearbox? Was it Webster? Almost certain it was not Hewland, but don't know. Why don't the MK5 gears fit? Is it that the layshaft doesn't fit?

Brian

[pahillclimber]

Brian,

FM has a VW transaxle that was machined to take stardard Hewland/Webster Mk9 gears. Mk5 and Mk8/9 share the same Vw transaxle, except the Mk5 has a larger diameter and stonger layshaft. You can remachine a MK9 to accept Mk5 gears, only downfall is it will no longer take Mk8/9 gears.

Rich

[Brian]

Actually, having owned two of them I know that any MK Hewland can run MK5 gears with no machining required at all. They are completely compatible as long as you install the matching layshaft. I had a MK4 Hewland with MK 5 gears in my old Merlyn MK6A sports racer, and I have a MK9 Hewland with MK5 gears in my current NTM B/SR. That is why I was surprised that the FM gearbox couldn't run them. I thought that it must use a different style of layshaft than the Hewland type.

Thanks, Brian

[Darryl Wills]

from that a standard VW housing needs machine work to run Hewland gear stacks. The housings are already machined to accept MK9/5 gears. You have to put the entire MK5 or MK9 stacks but neither require any additional machine work...we just went back to MK9 gears in a box that was running MK5 gears with no problems.

[brownslane]

A simple answer; No! There is no way a Hewland Mark 9 or Mark 5 will handle the power from a twin-turbo 13B. You can build it any way you want. If you exceed 200 ft lbs of torque, you will puke it all over whatever pavement you are driving on.

Even FTR (which is what I want for my CSR) is right on the limit for 250 HP and 190 ft lbs. A turbo charged 13B will have at least 300 HP (minimum) and over 200 ft lbs.....it won't last!

A standard FM chassis will handle a ton of power; the suspension will not! Roll centres way off, too much weigh transfer, crazy roll axis, weird rear camber curves.....no way you are gonna have a quick, easy to drive car with 300 HP.

If I had money to spend I would work on the handling of the car, build a full-house 13B with fuel injection and make a ton of reliable, progressive horsepower. Have the Mark 5 blueprinted and refreshed, and check it every race for breaking gears. Rebuild it after every season, and you will just about have a reliable gearbox. Forget about Mark 9....it is not strong enough without the previously mentioned modifications.

YMMV

Tom

[Top]

I don't know the answer but Walt Wurzbach has been running a V8 mated to a Hewland for many years.

[pahillclimber]

Thanks, guys for cleaning up the gearing differences.

As far as turbo Mazda with a Hewland MK5, we had one running the hillclimb series with about 400 hp in a Reynard 84SF with a Sprint car wing. Moreck had 2 main problems; when the boost kicked in, tons of wheel spin and it was like it was shot out of a cannon and the second was the wing created so, much downforce that it bent the rocker arms.

Tim,

My advice would be to max. what you got before going any further and really learn the car in season 2. I know that you want FTDs, but a FM does have limits. Bowland is winning with about close to 300hp. I think you can get close to that with what you have.

Rich