June 23, 2018, 03:46:02 PM

Author Topic: FC 8.8 Service Bulletin  (Read 9421 times)

Offline frijolee

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FC 8.8 Service Bulletin
« on: February 18, 2014, 12:19:43 PM »
FYI to all users of Ronin's FC 8.8 kit.

We appear to have found one weak link in our 8.8 setup.  It's not actually with Ronin's parts but rather we've found two users of the Ronin kit have torn the factory ears off the Mazda subframe where the vertical link attaches at the aft portion of the subframe.

The ears in question are stamped sheet metal and maybe 0.090" thick with no other geometric support.  At the same time, having the Ronin 8.8's front mounting point further aft puts about 50% more mechanical leverage on this link and the ears in question.  Combine that with the relatively high horsepower many users of our kit are rocking and we have had two known failures.  It takes some time to let go, so we're assuming this is a fatigue issue, but we wanted to let folks know.

We've designed and have cut a large batch of 1/8" doubler plates which are available immediately.  We will be including these in all kits going forward.  They're intended to weld in around the perimeter of each ear.

In the meantime we'll be reaching out to known users of the kit via email, but it's something of a manual process hunting through prior orders since we've gone through several revisions of website.   We also haven't tracked which kits have changed hands via private party sales.  If you're a present owner of a Ronin 8.8 kit shoot us a line at roninspeedworks@gmail.com and we'll send you gussets free of charge.

-Joel
(for the Ronin guys)

Edit 4/8/14 Some nice pictures of the gussets before welding.



« Last Edit: April 08, 2014, 12:32:30 PM by frijolee »
LS2 stroker FC, Mandeville big brakes, widebody, etc
Build thread:  http://www.norotors.com/index.php?topic=1274.0
www.roninspeedworks.com

LargeOrangeFont says: "Joel is right, and I love Joel. But his car sounds like the wrath of God."   ;)

Offline ebdyguy

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Re: FC 8.8 Service Bulletin
« Reply #1 on: February 18, 2014, 01:49:58 PM »
Has either of the two failures also been carefully examined at the upper attachment to the body for the vertical link?  Depending on what the forcing function behind the failure at the subframe really is, the upper link attachment point may also be experiencing an overload condition as well.

I am not saying that there is a problem there.   It is just that it should be looked at since failure was seen on one end of the connection which in turn suggests that similar loads (equal & opposite) would be present at the other end of the link.

Offline digitalsolo

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Re: FC 8.8 Service Bulletin
« Reply #2 on: February 18, 2014, 02:09:08 PM »
FWIW, the upper link area on the chassis there is relatively reinforced.
Blake MF'ing McBride
1988 Mazda RX7 - Turbo LS1/T56/ProEFI/8.8/Not Slow...   sold.
1965 Mustang Coupe - TT Coyote, TR6060, modern brakes/suspension...  project car
2013 Focus ST3 - Stage 1 BPU

Offline MoparX

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Re: FC 8.8 Service Bulletin
« Reply #3 on: February 18, 2014, 02:15:12 PM »
The upper mount looked unharmed in mine, it's much more reinforced than the lower mount.  The only thing I noticed about the stock link bar was the rubber bushings seemed to be pretty torn up, but I can't say for certain if the cause is due to the added stress from the  8.8.  I thought about doing an adjustable link with helm joints but I wasn't sure on the benefit so I decided to use a spare stock link I had instead.

On a side note, does anyone know if replacement bushings are available for the stock link?
« Last Edit: February 18, 2014, 02:57:18 PM by MoparX »
Well, it used to be MOPAR powered...............

Offline theantirotor

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Re: FC 8.8 Service Bulletin
« Reply #4 on: February 18, 2014, 02:18:46 PM »
My car is on stands in the garage right now so I will slide under it tonight and give it a look.  I am using an aftermarket Racing Beat latteral link, but I have it set to stock height and am not using it for camber adjustment.
:bacon:

Offline ebdyguy

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Re: FC 8.8 Service Bulletin
« Reply #5 on: February 18, 2014, 04:46:20 PM »
FWIW, the upper link area on the chassis there is relatively reinforced.

Understand that for sure, but you are now greatly increasing the lower attachment reinforcement which has the potential to move the problem to the other side of the link. 

It would be interesting to get some GoPro video down there under launches to see what is actually going on.

Offline digitalsolo

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Re: FC 8.8 Service Bulletin
« Reply #6 on: February 18, 2014, 04:51:12 PM »
No argument from me.  This is always a game of find the next weakest link.
Blake MF'ing McBride
1988 Mazda RX7 - Turbo LS1/T56/ProEFI/8.8/Not Slow...   sold.
1965 Mustang Coupe - TT Coyote, TR6060, modern brakes/suspension...  project car
2013 Focus ST3 - Stage 1 BPU

Offline largeorangefont

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Re: FC 8.8 Service Bulletin
« Reply #7 on: February 18, 2014, 05:45:28 PM »
I have not done any drag style launches, but mine is looking ok far. I am morbidly curious how long mine might last since I run solid everything, and a aftermarket heim joint sublink. I do shift very agressively on the track though.. in fact I probably should tone it down a bit. My co driver ran with me last time out and he didn't even think I was lifting to shift (I was..a little).

 I have a track day this Friday, but will probably get the new plates welded on next week. If mine did let go it would be at an inopportune time.
Quote from: cool
Sell it to spacevomit.  He'll finish it.

Offline theantirotor

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Re: FC 8.8 Service Bulletin
« Reply #8 on: February 18, 2014, 05:48:01 PM »
Email sent.
:bacon:

Offline kartermdb

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Re: FC 8.8 Service Bulletin
« Reply #9 on: February 19, 2014, 11:40:02 PM »
I have yet to install mine but can you tell us what kind of power both cars make and what they were being used for?  I am curious as to their application.

Offline MoparX

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Re: FC 8.8 Service Bulletin
« Reply #10 on: February 20, 2014, 11:23:00 AM »
Street/strip, 10k+ street miles, 250+ strip passes, approx 325 whp. 

Even though my car is down on hp compared to most on this site, my combo is biased towards drag racing and works fairly well for what it is.  I agree with the faitigue theory, it took almost 2 years for mine to break but a high hp car would probably have it happen sooner.  There just isn't much to the stock brackets.  Here are some pics from my car.






I used Mazda Comp mounts with my install and when it broke this is what happened. The u-joint ate up my old pinion snubber and you can see where the driveshaft rubbed metal to metal.  Glad I used rubber mounts that had some flex in them.



Here you can see my (not by Ronin) replacement brackets made out of 3/16" steel plate.  I welded in the stock bracket to help me line everything up and you can see how dinky it is compared to the reapair.



Even though I already knew about the plan to update the contents of the kit and send out brackets to all existing customers, I was glad to see this service bulletin.  Good example of a company standing behind their product.  :cheers:
« Last Edit: February 20, 2014, 11:54:17 AM by MoparX »
Well, it used to be MOPAR powered...............

Offline gc3

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Re: FC 8.8 Service Bulletin
« Reply #11 on: February 20, 2014, 01:59:09 PM »
has anyone ever seen this sort of failure with the stock diff?

Offline MoparX

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Re: FC 8.8 Service Bulletin
« Reply #12 on: February 20, 2014, 02:05:28 PM »
No, the mount for the stock diff is much more forward on the subframe and doesn't put any stress on the link bar.
Well, it used to be MOPAR powered...............

Offline RX7V8Builder

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Re: FC 8.8 Service Bulletin
« Reply #13 on: February 20, 2014, 03:03:32 PM »
Email sent for a set .


'87 Base Model FC
LT1 385 LE ported DART heads_ T56 
8.8 IRS
Ricardo

Offline frijolee

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Re: FC 8.8 Service Bulletin
« Reply #14 on: February 20, 2014, 03:27:07 PM »
In case it's not obvious, MoparX was one of the two failures we know about.  After we posted this one more gent came forward saying he'd found the start of a crack so we do want to get these out to folks.

has anyone ever seen this sort of failure with the stock diff?

Generally rotary guys rip the front interface to subframe off first.  That said, in doing a little asking around I found at least one guy who failed the ears in question with a T2 rear, so it does happen occasionally.  What all the guys making big hp rotary guys with stock rear ends have failed, you'd have to ask them because I haven't run across much as most of the really fast cars tend to be pretty tight lipped.

No, the mount for the stock diff is much more forward on the subframe and doesn't put any stress on the link bar.

It's less stress, but definitely not no stress.  The stock Mazda diff still has a significant lever arm on the subframe (best guess it's 8 inches or so), so there will be uplift and a load which goes into the subframe link as it tries to pivot about it's two front mounts.   That said, our lever arm is probably closer to 12 inches so as mentioned we're seeing a bit of increase in the lever arm mounting further from the pivot (which still has to be reacted by the link) so we put a little more stress on these ears for the same horsepower.

Doubler gussets should solve it without issue.  We use a significantly taller cross section and ours won't have the stress riser of the transition to box section (there's actually a notch there on the stock ears!)
« Last Edit: February 20, 2014, 04:19:55 PM by frijolee »
LS2 stroker FC, Mandeville big brakes, widebody, etc
Build thread:  http://www.norotors.com/index.php?topic=1274.0
www.roninspeedworks.com

LargeOrangeFont says: "Joel is right, and I love Joel. But his car sounds like the wrath of God."   ;)