LS1 V8 fd conversion progress thread

[stylus350]

I had it done by a guy in Canada who was doing a small group buy of his design to mount the diff, which apparently should stop any axel tramp so the diff has a fighting chance of surviving.

There is a thread somewhere where another ls1 owner strapped a web cam under his car looking at the rear subframe during some hard launches and you would not believe the amount of flexing going on.

I would be very interested to see that vid!

Good work by the way.

[MikeLMR]

how much of the flex is due to the frame being loaded in a way that it was not designed to be (sans power plant frame) and how much was down to the increase in torque? You have to remember the FD was engineered to be light and what you end up with is a structure that will flex if you take it much beyond what it was designed for

I like the tube work on your new frame, it\'s very neat, how does the clamp on the nose of the diff work? I guess it looks like that because the PPF bolted to just one side.

[tinker-27]

its not all the diff that causes axle tramp,ive been running mine mounted into the rear suspension for 2 years now with no probs, they do still tramp a bit but i dont know any cars that dont.keep up the good work !!

[MikeLMR]

axle tramp is to do with suspension geometry most of the time, most multi link setups are quite poor apparently. I\'ve not really looked into it but I remember skimming through a section on it on a book about chassis design.

[Spartacus]

I would be very interested to see that vid!

Good work by the way.

Here is the link to the thread (http://www.v8rx7forum.com/v8-rx7-technical/41391-psa-serious-concerns-about-safety-jimlab-cobra-cradle-4.html), but after coming back to it since I read it originally I now realize it wasn’t about the Mazda subframe but a custom made cradle to mount a cobra diff in a FD. There was the suggestion to try the same filming on a standard Mazda backend and on a Torque arm equipped FD but by the look of things it never happened.

[Spartacus]

how much of the flex is due to the frame being loaded in a way that it was not designed to be (sans power plant frame) and how much was down to the increase in torque? You have to remember the FD was engineered to be light and what you end up with is a structure that will flex if you take it much beyond what it was designed for

I like the tube work on your new frame, it\'s very neat, how does the clamp on the nose of the diff work? I guess it looks like that because the PPF bolted to just one side.

I completely agree with your first comment, but I’m not sure that you would want to design out all of the flex anyhow, as isn’t it a good way of absorbing energy over an a relatively long period to be released slowly rather than a short sharp shock which may break components? It would also be interesting to see how much flex there is on the backend of a standard FD.


This arrangement keeps the original diff mounts at the rear and replaces the Mazda  ppf at the nose of the diff to support and attempt to limit any twisting of the diff. The diff only has a significant mounting on one side where the ppf was attached so this arrangement is meant to use those points in the main but attempt to spread some of the load across the flat of the diff nose by using the clamped plates underneath.
Time will tell as to how effective it is.

[Spartacus]

its not all the diff that causes axle tramp,ive been running mine mounted into the rear suspension for 2 years now with no probs, they do still tramp a bit but i dont know any cars that dont.keep up the good work !!

I don\'t think that the diff causes the tramp but it certainly seems that tramp is the cause of many diff breakages, so anything that limits the tramp must help prolong the life expectancy of the diff.

[mar71n]

Have you bought the Hinson RHD exhaust headers, if you have can you post a picture.

[Spartacus]

Yes I bought the whole exhaust system from Hinson\'s (still waiting for the back box:Yawn) , not cheap but it is stainless steal and saves a lot of trouble trying to get one made without a pattern.

[Spartacus]

Couldn\'t resist it, as I\'ve just taken voluntary redundancy after 26 years in the same business, a little treat for the old girl (the car that is).

[mar71n]

Having just cut & welded my headers from a box of bends, those look sweet

[Spartacus]

If I could have done what you have, I probably would have and saved enough for an ls2:Thumbs-up

[CRAIG R]

Whats the reason for the inward kink at the lower end of the nearside header??

[Spartacus]

If you mean here, I have no idea but I have just loosely assembled the Y pipe the way it looked liked it wanted to be put together just for the picture. It may be completely different when I come to put it on the car.

[Grub2000]

Have you thought about getting a few exhaust sets made up over here, based on the Hinson ones? might be able to flog em and get back some costs.

I had a dream last night, that I had ordered some bits from Hinson and that I was on the phone to him asking about the intake system....then I woke up...nooooo