Franken44 Track Build

This is very, very cool.  I'm not sure how I missed this thread earlier but I'm glad I found it.

Let me know if you ever want to chat aero; after data analysis/coaching, aero development is probably my second most-commonly discussed topic with clients of mine (though few in the amateur community seem interested).  And in many classes (like ST or GTSx) it can be more important than shock tuning or power output.  Considering its potential complexity, it's easily the most opportunity-rich area in amateur racing.


Have you found many books on the subject?  There are some terrific resources on aero development I can recommend in case you haven't found many.  Perhaps my favorite "starter" book is Simon McBeath's Competition Car Aerodynamics.  He's supremely knowledgeable and thanks to his contributions to Racecar Engineering (the mag), he's very easy to get in contact with.


Anyway, lots to talk about!  Quick question: it's tough to tell from the pictures but is there a noticeable transition in the diffuser floor where does it go from being flat (throat) to increasing height (diffuser)?  It looks like the floor starts low at the front and is simply a linear increase to the rear of the car?


Exciting stuff!

Well, the first outing with the flat bottom was a bit of a bust. A rubber exhuast donut between the car floor and the drop bottom reached it's flash point, and started a fire underneath the car as I was pulling into the pits, which in turn lit some of the undercoating on fire. It turned out to be just a "brush fire", but the flat bottom had to come off for the weekend. The 4 foot deep splitter seemed to be effective.  

I will be looking into ceramic coating the exhaust, and more heat shielding. I'm not sure I'll get it done before Gateway in 3 weeks, though it might be nice to try on the roval.

Very brief fun clip from the restart of the weekend:
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Not the most tidy driving - overcooked some corner entries - still learning the track and the car.

I have been doing a lot of research, and have a 26 page (and counting) thread on Rennlist here, if you have a few hours: [You must be registered and logged in to see this link.]

I may take you up on talking some aero in the future.

There are always teething pains when you make major changes   Still a good idea.

I had hoped to race at NCM last week, but just couldn't make it.  I will be there this week with Bluegrass BMW, I'll be teaching the novice class and driving there for my first time.

Bummer, it would have been good to compare notes. We will be back at the end of the season - hope to see you there!

The fire was briefly exciting, but small, and rapidly put out. I finished the weekend just, fine. Sunday was sketchy in the rain, though.

It's a crazy track. Continuous corners, and elevation changes. They are getting very serious about the noise issue. Must be at/under 103. That said, my unmuffled LS passed apparently under 100 DB (amazingly). The key was to have the exhaust pointed to the inside/passenger side.

I never answered the question on the diffuser. It stays flat from the splitter to just behind the B-pillar, and then goes up at about an 8 degree angle from there. Hard to see the inflection point, but there is one.

Sterling Doc wrote:They are getting very serious about the noise issue. Must be at/under 103. That said, my unmuffled LS passed apparently under 100 DB (amazingly). The key was to have the exhaust pointed to the inside/passenger side.

Saturday was severely overcast and cold and I hit 102.3 decibels. Sound meter was at T3, where i was going wide open in 3rd. Sunday was clear and sunny, no one came close to blowing sound.

The first real experience with the (developing) aero package was at Gateway this last weekend. We still need to add the vertical elements to the diffuser, but the car was excellent subjectively, and fast, going well under the existing track record to TT2, and trading fast times with a supercharged, flat bottom E46M3 (also on home-grown aero). Gateway has pretty mild banking (9 degrees), but we saw 1.7+g's on fairly little 245/40/17 Hooser A6's (size compromise by rules, until I can get it detuned a bit to fit into the class, or add weight). The car felt planted. We only got 3 sessions in before the spindle/knuckle broke, but already had the pace for an overall win (bench racing the subsequent race we didn't make). Very promising!

Next event is a Road America, which will be the first event where can compare directly with last year. The 1st two events have been at new tracks - NCM, and Gateway.

Now to look into the spindle failure. It looks like it was cracked for a bit, based on the appearance (see pics below). I will check the other side tonight. I have the High Strung arms, with the extended 19mm pins. I am wondering if the extended pins are overstressing the mount on the knuckle, that is weakened by drilling it out for the 19mm pin. I will be looking into my options before Road America.

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Unfortunately this ended out weekend early:

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Hey Eric,
car looks good, I like your home grown aero. We are about to build a E36 for WRL enduros
and home grown aero is free so I am interested to see your results from Road America.
As for the spindle, man you got lucky that wheel didnt come all the way loose.
As for the pic, ya it looks like it had been cracked a while. After reaming the hole to accept 19mm pins
the torque on the pinch bolt is going to be critical. A little over tight, especially if it was taken apart
and put back together a few times, could lead to fracturing the casting. I think the factory torque
spec is only like 30 ft. lbs. It also looks likr the gap in the part of the spindle the bolt goes through
has been closed up due to over tightening.

Good point, I may well have been over-torquing it!

I'm guessing there is not a longer, 17mm (stock OD?) pin HD ball joint available for your High Strung arms so you don't have to drill the spindle? I'm just thinking I'd rather replace ball joints every season vs worrying about breaking modified spindles. What does the Racers Edge billet arm require you to do to the spindle, if anything? They say it's a 2 piece pin design with a beefy 0.9" OD, but it doesn't mention drilling/reaming the spindle.

Most pin failures I've seen are pretty dramatic. This was at least a slower process. It was clearly cracked for a bit, and held up for at least a weekend cracked. I think I'll be OK with frequent inspections, and timing it out after a season or so. I don't know about the RE stuff.

Hey Eric, where do you get the sheets of plastic? And what thickness is that?

Menards

1/4" high density polyethylene. In the plywood area. Great stuff!

TAP Plastics is local to me, but they do ship. The ABS is a little more expensive but lots of thicknesses and it's black. I used it for my fog light covers.

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I had a bellhousing failure at Road America this last weekend. Just pushing in the clutch was the final straw - likely stress cracks from the stresses of racing. Just ordered a Quicktime SFI rated bellhousing. Amazingly, they make one with the 944 torque tube adaptor built in! It should be a lot stronger.

I am going to have a C5 BH adaptor, and clutch slave for sale!

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Ouch, that must be very frustrating .. especially after what happened at Gateway.  Really sorry to hear you had another bad weekend.  That pressure plate looks to be a mess.  Any idea why it is so deformed?

The QT bellhousing is a nice piece, heavy but mounted low and mid. Not sure how "stresses of racing" cause this failure unless you mean banging shifts in the heat of competition. Seems like something easy enough to avoid even when racing.

Rich

So, we take a uni-body and go over curbs/rumble strips, accelerate, brake, create excessive Gs and repeat, repeat, repeat. This creates huge amounts of body flex even if you have a full cage. Then we add a solid torque tube/transaxle drive train and mount it to the body in a sprung weight fashion and it can’t handle the flex.  That’s one of the "stresses of racing".

I've have both motor mounts bushings go - likely causing a lot of twist, and the trans is solidly mounted as mentioned above. So this may have been a chain of events. The passenger insert was just gone - disintegrated, and the driver's side was cracked. I drilled out some suspension bushings the had the corrected OD for a press fit.

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It's possible that the clutch PP bent first, but it looks like it was collateral damage, spinning through the shrapnel.

Just to be on the safe side, I also got an aluminum PP & 4 puck clutch while I was at it. It's slightly smaller than the original Spec stage 2 clutch, and quite a bit lighter - which should speed up the slow shifts. Put a dent in the racing budget, though...

I can appreciate what you're saying about the weight of the Spec clutch kit.  My Spec stage 1 for the 928 swap feels like it weighs considerably more than the Exedy twin disk I had in my Evo.

You may want to consider adding back some flexible bushings in your transmission mount set-up.  Without an incredibly stiff chassis, there is likely going to be a differential in the movement between your car's unibody and driveline parts.  I can't remember, has your car been seam welded to stiffen the tub?  Although I'm not sure even that would reduce flex enough for solid mounts with the kind of power and grip you have.

Another thought is that the rule of thumb for solid mounts is generally everywhere or nowhere.  The exception would be a differential or rear axle separated from the rest of the driveline by joints and couplers that allow for plunge & flex.  Even then, fully solid mounting the driveline turns the components into stressed structural members; typically not an ideal situation for off the shelf, consumer grade "structures" that contain lots of fast-moving parts with really tight mechanical tolerances.

I had bushings in the motor mounts disappear on me too. My trans mount is a urethane filled stock unit, so maybe that's what saved my bellhousing. Interesting thoughts on the clutch fromTony but I agree it was likely collateral damage. Glad to hear you've got it figured out, thanks for sharing and wishing you the best.

Rich

A few of you guys had motor mount bushing issues. What material are those made out of? Rubber, vinyl, urethane?

I would guess urethane. The bushings in my 2015 mounts failed but the ones in my original 2011 mounts were fine. I've now got the old bushings in my new mounts and all is well. My guess is TPC changed supplier at some point.

Rich

I would guess Urethane as well. They seem somewhat brittle. I have the solid inserts on order. I hope they come soon!

The new clutch, bellhousing, and ancillary parts are all in - will start to go back together today.

The Quick Time bellhousing looks and feels like it could be the hatch off of an M1A1 Abrams. I'm pretty sure it will be the last thing on the car to break moving forward.

Had fun on a spontaneous open track day in Feb at Gingerman!
Car is now for sale - see the FS forums.

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-$29K OBO
-Built for cost effective, serious speed!
-Can race NASA ST1, or ST2
-Makes over 500 (crank) HP on pump gas, and 400+ lb/ft. torque everywhere, reliably.
- Only 2 weekends on new LS3 crate motor (not a junkyard takeout) with built LS1 heads for maximizing compression & torque.
-50/50 weight balance, easy on tires.
-6 piston Titanium piston Wilwood brakes - no fade, and pads last more than one season.
-$89 brake rotors
-Wilwood dual master cylinder pedals (manual brakes) with adjustable bias
-Triple adjustable JRZ shocks rebuilt by Tim Olsen, coil over conversion, tubular front a-arms.
-Aluminum flywheel and clutch (Spec stage 2+), revs fast and shifts fast!
-Hanksville Hotrods roll cage with extra door bars, and tied into shock towers.
-2nd at ST2 at NASA Nationals, has lead the NASA Great Lakes Thunder races overall.
-Ready to race, and will be racing in a couple of weeks at NASA's NCM race.

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