2005 25 hour prep - struts/exhaust/3rd link/motor

[Marcus Miller]

After freezing my A** off at the 25 hours of Thunderhill, I've decided next year will be infinitely better if I'm driving rather than spectating.
I'm looking at upgrading my Pro7 to a full IT suspension, to take better advantage of the class rules I'll running under (E2 - pro7, ITA, SM, Honda Challenge). I've been doing some reading of the archives and didn't see the answers to these questions:
A) Has anyone run Advanced Design struts with great success? I know Jim Susko sells them as does GC. They are quite pricey compared to a Koni or Bilstein. Follow-up to that: If you were running a 25 hour race with several 4 hour enduros prior to that, what struts would you choose and why? Remote Reservoir is legal, but budget prohibitive. I'm mostly worried about longevity. I already have a fresh set of Pro7 spec Tokico's; that solution would be the cheapest....

KC Raceware vs. G Force vs. ISC 3rd link. Is there a lap time difference? Is there a strength difference, or is the installation the most important item? Do any of them have known failure points that are likely to occur prior to 40 hours of running (assuming few to no off track excursions)? Follow-up to that: How much quicker / more comfortable will the 3 link be as compared to a stock 4 link with a panhard instead of the watts? I saw a reference to 2-5 seconds a lap, but not sure what the other side of the comparison was.

C) 98 Db limit - possible to hit with a full ISC exhaust? Will an SDJ header provide anything the ISC doesn't? I'm thinking over the course of 25 hours that quieter is better, assuming we are not killing the motor with muffling (Supertrapp)

D) Fully prepped ITA motor- I assume 25 hours is well within the lifespan of one of these? I'm looking at the ISC version as listed on Mike's site. Who else should I be looking at? I've got Mobius on the West coast as well as Haag. What do the fast Nor Easter’s run?

Thanks guys! This will be a fun year, prepping for this....
Marcus


[This message has been edited by Marcus Miller (edited December 08, 2004).]

[This message has been edited by Marcus Miller (edited December 08, 2004).]

[lateapex911]

First, the shocks...the ADs are not bullet proof..I have heard of, and have seen failures. You need to get the guage and special filler as well as a source of nitrogen, as they are reported to leak.

On the other hand, Susko sells them and they are valved to his specs.

And...I just don't think Tokikos will run that long without giving it up a bit. I've seen them fail and bend as well, mysteriously at that...(No known impact, but just a little bent)

Also, the 7 is better off if run at a low ride height, and with good body control...stiffer springs are desirable. But 350 or so seems to be the limit for the Tokikos.

So........the ADs are probably a better choice. The strut housings are stronger to boot. You could go the custom valved koni route probably, but i bet that once you do, the ADs will look cheap! In the world of dampers, they are not that expensive. Nor are they the best...I'm still trying to decide if they are a good "value"...but compared to dampers that are $1000 a corner, they look pretty good...

Some general comments on the tri link concept.

In general, I would advise going to the panhard rod/"traction" link (Tri link) setup, as drivability is much better. I think that an RX-7 can be hustled around at fast lap times without it, but not lap after lap. And, as you are looking to run 25 hours with all sorts of "events" occuring on track, you need a "forgiving" suspension. Suskos stuff is at least second generation, and has seen revisions to add strength. Heis a former GM engineer, so his suspension knowledge should be stout. His stuff is designed to work together...the tri link and the panhard and the front strut spacers all work to provide favorable roll centers and so on. If you are going this route, he deserves a call. (You will also hear a story here about how a part he sold to another former engineer who races and posts here didn't fit. I can't explain that, all the stuff i've gotten from him has fit....I wish I could say that about all the suppliers I've dealt with....)

I HAVE had a panhard rod rip out...but that one has been greatly revised, and wasn't from Susko. I like Mike V. too...I had his header on my car...it's a sweet piece. His exhaust stuff seems pretty sound.

98db? Hmmm ....thats close. I am 98-99... I run a twin pipe straight under the axle to a 3" collector and through a big Dynamax (?) "muffler". If it muffles, you could have fooled me! I imagine I could get my car down a dB at any track with a turning elbow, but that's very close...too close for comfort. If you can add some weight, the Racing Beat presilencers might be worth a look.

25 hours should be no problem with a well built motor. Make sure it is solid, with flat side plates and new housings, that it pulls even compression, is made from balanced components, and it has been broken in. Keep it cool, and keep the wild over revs under control, and you should have no problems.

I'm not the paragon of speed...and run a non pro built motor, but I understand that ISC and SDJ are both solid builders.

Be prepared to go through brakes and bearings. I was in charge of this aspect of a 2 car RX-7 team at the "longest day" at Nelson Ledges for 2 years. The first year we learned that both cars had the brakes go with a lap or two of each other at 12 hours, and both front bearings went within 5 laps of each other at 18 hours. So the next year, to save time and get fresh shocks on the car, I had 4 struts all made up with fresh bearings and brakes and dampers. At 12 hours we brought the first car in and just swapped the whole thing. Saved a ton of time, and it was scheduled, so it went very smoothly. Then we did the 2nd car. We went on to win, by about a minute. We had lost the previous year by a few minutes...the time we spent doing the bearings.
Try to think through the race and schedule stops proactively rather than reactively.

Sounds like fun...I wish I could do the event!



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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[ddewhurst]

***(You will also hear a story here about how a part he sold to another former engineer who races and posts here didn't fit.***

Jake, not a story. FACTS, the written instructions are for 1/2 inch holes for 1/2 inch bolts, the strut spacer is alum. That Jake is what is called line on line fit. When the holes in the strut spacer are .025 inch different center to center than the holes in the strut most normal people start measuring. IIRC his instructions say use a die grinder to open the holes when the bolts don't fit. With the .025 difference that would be called something a whole lot tighter than a line on line fit. Please don't get your word story mixed up with fact. Now & then someone starts a thread about parts peddlers who do not service their customers & many people tend to frown upon the parts peddler. Hey, if the guy would have stood up to his ERROR & supported his customer I would never have said a thing.

Have Fun
David

[Marcus Miller]

Thanks Jake and David!

Jake, on the parts:
Shocks - Any idea on how do the Bilstein's measure up?

I had forgotten springs in my original post; they will definitely be upgraded from the Pro7 specs.

3rd link set up- I have only seen pictures of them; are the mounts between the three listed substantially different?
Was the Panhard failure related to the installation, (mount failure) or did the bar physically fail? Carrying a spare bar isn't that hard, rewelding the mount might be.

98 DB is rather rough, but we might disturb the cows, you know....
I currently run the same Dynomax you mention I think. I'm at 87-89 DB with stock maniold and 2.5 inch exhaust. I'm leaning to wards just ordering Mike's setup and going from there, be it sound elbow, or whatever. I know the SM guys have had luck running multiple mufflers, similar to RB's Presilencer. Iwas thinking one of these:

Motor will be pro built, I don't have the time in the next year to fully understand and learn to build my own rotaries. Break-in will be done on test days and such leading up the the event. I also plan to run several shorter (4 hour) events in the lead up to the 25 hours

I like the idea of prebuilding corners of the car. Did you have the full coil over set-up built? Or did you swap the strut over from old to new?

Are you sure you can't do the event? I've only got two drivers right now...

Marcus

[This message has been edited by Marcus Miller (edited December 09, 2004).]

[mustanghammer]

Marcus,

I use a Dyno-Max bullet muffler and make sound in MiDiv.

We buy these mufflers new, cut a hole in the side and pull out all of the fiberglass packing. We then replace the glass with lava rocks. Ya, just like the ones in a gas grill.....used grill rocks smell good too! To seal the muffler back up we use 16 gauge steel and steel rivets. A little hi-temp RTV and you have a leak free deal that is serviceable.

We do the same thing with the bigger Stainless Steel Dyno-Max mufflers on EP cars.




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Scott Peterson
KC Region
IT7 #17

[Tak]

Marcus-
Have we met? I run the #29 rx-7 in ITA with SCCA (white, blue doors).

Anyway, go with the G-force tri-link. Structurally, it is superior to the others. I built my own panhard bar, so I cannot comment on his. I ran for several years with the stock 4 link (with pro-7 'loosening') and a panhard bar. The tri-link is results in much improved rear stick. At least 1 sec a lap worth. Would be more but I'm struggling to get my front end to stick...
I did not like the hardware that came with the tri-link. Buy slightly longer grade 8 5/16 bolts, sae washers, and nylock nuts (nuts and washers don't need to be Grade 8). The standard nuts and lockwashers that come with it will loosen up. Unless you are a very good welder, have the axle mount professionally welded. I also suggest breaking all the sharp edges on all of Jims parts.

On the panhard bar--gusset heavily. Add re-inforcement that links the frame rail, panhard mount, and unibody all together. Lots of weld or rivets. And still inspect freqeuntly (try to shake the back of the car sideways--if there is slop, something is loose or cracked).

On shocks, there are some very reasonable double adjustable Koni's available for ~200 a corner. Fronts will require significant strut modifications (I think Jim has those too). I have also seen AD shocks leak and fail, so I have no confidence in them.

The stock exhaust manifold is very good at noise reduction. Any header will transmit MUCH more sound (and heat) to the muffler. Mufflers must be stainless to last. Stainless steel wool packing or Lava Rock both work well. The key to sound damping is large volume. Buy the biggest muffler that will fit under the Rx-7 body. I run an 18" long by 7" diameter 3" flow pipe muffler and record a consistent 99 dB with a turn down (SS wool packing). With a header, fiberglass packing will only last ~4 hours.
On the motor front, look outside of CA. 2 of the 3 builders I would trust are ill, and the 3rd (Paul Erje at Rotorsport) has stopped building race motors (I believe).

25 hours is no problem for a properly cared for motor.

Tak
aka Tachi Callas

[Marcus Miller]

Thanks for the advice on sound guys!
Scott, I had heard of the Mazda Comp lava rock mufflers and never really pictured how they were consturcted. Your home made muffler sounds like a great idea.

Tak, we haven't met yet. I'm sure we will meet at an event soon I ran with N*SA most of the year, and CalClub during the back half. This coming year I will likely be spending time getting my brother ready for the 25 hour, and running minimum's with SCCand NASA to keep my license current.

I actually don't weld, so will definitely need a shop for the install. (and I need to learn to weld before the 25 hour next year) Do you have anyone here in Norcal that knows ITA 7's (and hasn't moved on to SM ) that would have experience welding it up?
The mention of gussets and braces is why I would prefer someone with experience to do it. Everyone I know runs/ ran pro7 where such goodies are not legal.

I'm leaning against the AD at this juncture. The Koni's require a larger diamter strut tube, correct? I'll have to look into these, as well as fit to the camber plates up top (GC).

On the motor, I'm thinking of an ISC built motor, though freight from FL might hurt.

Thanks!
Marcus

[lateapex911]

Marcus, shoot me your email, or use mine...

------------------
Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[dickita15]

just a note on the g force tri link. i have installed three of these as they have been improved as time goes on. the newer ones have large bolt where it attaches to the body and where the link attaches to the front mount is now in double shear. It is now a very good piece.
dick patullo
ner Ita rx7

[miketrier]

I suggest going 100% with the ISC setup. Carb, distributor, engine, suspension, exhaust, etc. Mike's parts fit and work and are very strong. I have have had his 3rd arm setup for 5 years without a problem. I personally have many of his parts on my car except I do have the SDJ header with 3" over the axle and it seems to do very well in the power category but I can't say if it is superior to the ISC header. I have the Dynomax Ultra 17296 3" muffler (NAPA) and have never had a sound problem. Hang the exhaust with chain.

[Tak]

Yes, the good Koni's will require larger strut tubes. Pain in the A%& to make. Next time I'm buying them...

Tak

[Brad]

Have Rob @ pineappleracing.com build your motor. He knows his stuff and freight from Portland is less than you think.

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--Brad--

[Marcus Miller]

Somethings are starting to come together, and the letter from Mike V helped that decision making process Thanks Mike! you'll be hearing from me shortly after the holidays.

Last decision; struts/shocks - I think I'm down to Koni's or Bilsteins. Thought's specifically on those two?

Marcus

[[email protected]]

7sOnly in SoCal has developed an new strut tube that might be your answer. It will take a larger strut and is designed to replace all spacers. They also have designed new control arms to completely remove bumpster. Call and ask for Tom for full details 1-661 746-5456.

[Marcus Miller]

Hey Shawn,

Tom was showing me the prototype (or first production run?) for those in November; I wonder if I can fit those in the rules...
Hope your weekend went better than mine... (3 laps, cooked the motor and went home saturday.. got home and saw your post on the Calclub about having a motor at the track for sale.)
Marcus

[[email protected]]

Not as bad as yours but we did have some major carb issues that keep the car in and out of the pits all weekend.

I saw that you had popped the motor on fri but I had already sold the 12A.

2cents-Have Moblius Motorworks build you a race motor and run it for years!

[Chris Taylor]

One thing I didn't see mentioned was rear tire wear. After installing Susko's tri-link on the rear of a customers car, the rears now wear evenly. That's a nice trait in an enduro, for sure!

The fronts on the other hand... well, they'll cook a set of Hoosiers in two races.