Check out my reinforced PPF
 

In my ever going attempt to solidify my drive train and eliminate wheel hop, I’ve just reinforced my PPF. But first a little back ground on some of the little things I’ve already done.

I have the Jim Lab nylon diff bushings. These stiffened things up nicely without any vibrations. Then late last year I installed new pillow ball bushings. Guys/gals if you have high mileage, it is an absolute must that you check and replace the pillow balls. I’m serious the car felt like it was brand new again and made the biggest and most noticeable difference. Also this combination has eliminated most of my wheel hop (but not all of it on the street). I then figured I would install some nylon bushings for the longitudinal arms to further help with the wheel hop. They did help some but not as well as I expected. However, the car did feel more solid. The only problem I had now was the tranny movement under hard acceleration. With everything else solid, I thought that my PPF may be cracked. So I removed it and to my surprise, it wasn’t. :confused: I thought why does it move so much then? With assistance from my dad, I grabbed two pry bars and we both began to twist the PPF from both ends. I was trying to simulate the torque twist of the engine (which we did). The PPF had a surprising amount of give. More that I thought was necessary! It would appear that Mazda really did design the suspension to load up. While the frame was out, I thought what the hell, lets reinforce it and see what happens.

I searched over the forum and couldn’t find any pics of anyone who had done a previous reinforcement.
This first pic just shows the frame in it’s raw state with some paint ground off in the sections that were to be welded.

https://www.rx7club.com/attachment.p...hmentid=167026

The next few series of pics just shows my approach and layout of the plates I was going to weld in place. There is a reason I did it this way and didn’t use a long solid piece.

https://www.rx7club.com/attachment.p...hmentid=167027
https://www.rx7club.com/attachment.p...hmentid=167028
https://www.rx7club.com/attachment.p...hmentid=167029
https://www.rx7club.com/attachment.p...hmentid=167030

Now you can’t tell by the pics but the PPF isn’t perfectly flat. That’s why I had to cut smaller pieces to fit in certain locations. Staggering the plates creating more weld points should make it even stronger than just one solid piece. Well at least that’s my theory. :D I welded each plate at a time as to prevent the frame from warping from all the heat.

Here is a pic of probably the best weld I did over the whole project. Don’t laugh to hard, I haven’t welded in over 10yrs and I was never an expert at it. However I finally did figure it out later but the project was almost done. Oh well! I did get plenty of penetration (which is what matters the most).

https://www.rx7club.com/attachment.p...hmentid=167032

Here’s a couple spots on the back side I did. For some reason the factory only welded certain sections on the back and not all the seams? :confused:
https://www.rx7club.com/attachment.p...hmentid=167034
Here we have the welded frame.

https://www.rx7club.com/attachment.p...hmentid=167037

Lastly the end result. I love how the paint hides the ugliness. LOL

https://www.rx7club.com/attachment.p...hmentid=167038
https://www.rx7club.com/attachment.p...hmentid=167040

Now the final test. With my dads assistance again, we grabbed the pry bars and began to twist again. The damn frame wouldn’t budge an inch. We were both struggling to make it twist this time. NO NADA! :D.

Now that’s it’s back on the car, all I can say is HELL YEA! This is how the car should have come from the factory. There are no unnecessary vibrations or anything. The car still drives smooth and not harsh. Now I need to check my engine mounts. ;)

nice work :)

just shows theres plenty more to improve in a 15 yr old design :)

wonder how this compares to the mazdaspeed ppf

very very interesting

Damn good work!!!!

congrats,
-josh

Any idea How much weight was added?

Every PPF I've ever seen break fails at the ears where it bolts to the diff; they break off. If that area isn't the one heavily reinforced you're not going to see much improvement.

^Was just thinking the same thing.
It is nice work, but now that you've removed any possible flex in the PPF, won't that just put more strain on points of attachment?

Very true- however if there is less flex in the ppf then the ears won't snap nearly as easily. I was concerned about weight so I just welded 90 degree angle iron on the inside corners of the ppf- It also worked very well and only added about 3 pounds.
John

nice boat anchor

That is some big ass grill :P Weird how no one else have thought of doing this to reinforce the PPF. Nice work :D

:scratch: that's what I originally thought too

I think not. If the PPF typically twists along its length slightly (which it does) absorbing some of the shock then by making the length of the frame stronger you concentrate the stresses even more at the mounting ears since they are the only parts that are flexing much now. I'm absolutely certain this modified PPF is stiffer than stock, but my guess is its fatigue life will be drastically shorter. It will feel great until it breaks in the same place they all do and it will most likely break sooner if its put to the test.

Next time you're at dinner pick up a fork by its ends and twist it. It doesn't matter how much you strengthen the stem of the fork, the weakest point (also the greatest concentration of stress) is still where the prongs meet the stem. That is where you're failure will occur even if you use a phone pole as a stem.

Here is one of the places that I welded on my PPF (Red circle). As DamonB stated The places that they tend to crack is on the fingers. I think I put 7-8 plates of similar sizes on mine. The brace that goes through the PPf even has marks on it from twisting so much from a busted drivers side motor mount.

https://www.rx7club.com/attachment.p...hmentid=167100

Notice anything else wrong with this pic?

You have a ventilated diff? Ouch.

Ding Ding, you are correct sir.

I think that from having a broken motor mount caused the PPF to start to crack, wich must of started some hair line cracking in the diff case. After making a solid motor mount, welding up the PPF, Drag slicks and sticky surface of a drag strip, sent the diff to meet his maker. Keep in mind I was only making around 340hp to the wheels at this time.

Thats why I used angle iron to stregnthen the ears as well. Still holding up after 5 years of HARD abuse.


[/QUOTE]Next time you're at dinner pick up a fork by its ends and twist it. It doesn't matter how much you strengthen the stem of the fork, the weakest point (also the greatest concentration of stress) is still where the prongs meet the stem. That is where you're failure will occur even if you use a phone pole as a stem.[/QUOTE]

I eat with my hands.. :) <grin>
John

mine completely broke all the way across where you have it circled.

i reinforced mine, but broke the diff a few days later, so no news on how it works

Did it brake in the same place as mine, Because all of my internals seem to be fine?

If the engine or diff mounts are worn much at all then the PPF is under tremendously more stress and of course the hop is much worse.

At last week's autox I had so much grip on the fresh race rubber that even with a 7000 rpm launch I could not break the tires loose; the car just went. I have a stockish clutch and as I tried more and more rpm it would slip a little as I stepped off of it but the car launched with no hop or vibration whatsover. Completely stock mounts and drivetrain with 240 to the ground.

Damon- that's correct you certainly know your sh*t. Your experiential knowledge is appreciated. All these little factors add up in these cars to one thing=wheel hop.
I got rid of mine by reinforcing the ppf, replacing the rear pillowballs and adding tein ha's
John

Good to hear. I would think the best way to reinforce it would be to weld generous angle or flat steel flanges perpendicularly onto the side of the ears along their entire length which is probably what you did.

If I were doing it I'd take some 1/8" steel plate (the blue and pink) and cut it into strips about an inch or so wide. The side of the strips that weld to the PPF would need to be cut to shape so as to mate with it properly and then I'd weld them to the PPF (green) as well as eachother where they meet at the rear. They wouldn't interfere with the bolts or the hole the chassis brace passes through and would make the weak area much, much stronger for little weight or work.

I know the pic sucks but just imagine welded on flanges sticking straight out from the side of the PPF.

sweet, looks good and must work great..

my actual differential is what broke. the housing is fine. all the teeth on the diff were flat

I would think that one piece would be stronger than welding smaller pieces in place. however, yours will still be stronger than the stock version. But I can't really back up my claim in strength, I'm not a welder by trade :) Either way, good job, looks killer

Thx! I don't know the comparison but the steel cost me $22.00. So I saved a bit doing it myself. I have a lot of steel let to do other stuff with.

Oh yea I forgot to add, I used 1/8" steel. I should have weighed the frame before hand. It's a bit heavier now. I would say is weighs 15-20 lbs more.