Which is "better", the Pettit unit or the one from Tri-Point Engineering? I am going to need one, or find a good stock unit, as I broke mine when I took it off to remove the engine.

 

Doubt if there has ever been a comparison one. But I use the Pettit one. Pettit is, as im sure you know, known for their high-quality parts. That reason alone is why i went with Pettit. Plus its an AST, as long as its not plastic you'll be ok.

 

I doubt theres much, if any of a difference....

 

Somewhere in the deep, dark recesses of the 'Net, in one of the numerous pages of things I read on FD reliability, I seem to recall that someone had related that only the factory AST did the job as intended, i.e. creating a stagnant coolant zone that actually separated the air out, and that aftermarket ones only imitated the design of the original. Something about the plastic ones having a special inner-chamber found lacking in the aftermarket ones?

 

The stock unit was rumored to have baffles, but when someone actually cut one open it revealed it was empty inside. The only differences between stock and aftermarket ASTs are the slight restrictions put in on the bottom outlet.

Taken from this thread, which has pics of an AST cut open:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/ast-dissected-433610/

As far as I know all aftermarket ASTs remove this restriction so an aluminum AST that maintains this restriction is the "best" AST, if one exists.

 

Thanks, BlueRex! I guess that answers THAT question regarding the stock unit, huh?

I wonder who makes that aluminum one shown in the thread post #10, by EFS.O?

 

The guys who sell datalogit had that pic i posted in their web page,but not any more...

 

Myth. The AST is not a swirl pot.

Given the fact that coolant enters from the side of the tank and exits from the bottom any air bubbles tend to stay in the tank since they can't exit out the bottom hose; they always float to the top.

 

No need for thanks, I'm just regurgitating what others have taught me .

 

Best AST was ones that RX7store used to sell.. It had billet Aluminum pressure cap neck.
The pettit unit has kind of weak cap neck and sometimes it bends and leak. I had one that leaked and I blame a little for my engine overheating and killing my engine.

 

I ordered mine from rx7.com and have been very pleased with it.

 

I cut a stock one open as well and laughed when I thought about all the threads I had read about the supposed baffles inside.

 

i had the same problem with my pettit ast. The neck for the pressure cap would not hold more that 7psi. My coolant would sometimes come out the over flow when i turn off the engine. I tested the pressure cap twice and it was fine, it was the stupid neck on the ast. It would be an easy fix if knew how to weld, you could order a billet al filler neck from summit for around $25.

 

I started with a Pettit AST which I later installed on my second FD. I purchased a tri-point as it was made out of a higher gauge material and used the stock size cap. There was nothing wrong with the Pettit AST it's just that i liked/preferred the Tri-point AST over the Pettit. Jack

 

i believe the pettit uses a larger cap than stock. my tripoint used the stock cap and had a restrictor in the bottom connection. the tripoints are also anodized black while the petit is greyish powder coat.

 

I got my metal AST from RX7.com too and has worked out great for me. Reason why the metal one is better, is that the stock plastic ones have the tendancy to melt and leak.

 

[QUOTE=RX-7racer88]I got my metal AST from RX7.com too and has worked out great for me.

He wasn't asking why the metal one was beter than factory, he wanted to know the differences between the pettit and the tri-power AST's

 

I have the Gotham Racing one, but as far as I can tell its the same as the Pettit, I haven't had any problems with it.

 

Picture of my Tri-point AST, not the factory small cap. The neck is much stouter than the Pettit (billit I believe) and the neck doesn't bend or move when your pushing down ton the cap to install or remove it. JAck


Here is the Pettit AST note the lever style and larger cap

 

I like this one that SpooledUp7 used to make



VERY Stout Polished Aluminum

 

i have that same purple tripoint ast. but it has a different cap.. is your cap oem?

 

My cap is OEM, I removed the bottom seal and am running Evans coolant at zero pressure. I think you can see the sticker on the cross over tube. Jack

 

has any body tried the Greddy AST tank?

 

I haven't but I've seen them and they are very nice bling bling and seem well crafted. Only question is will it work with an FD? Since I know they are car specific on their site unless they added one for the FD.

 

I just bought it and and was suprised that the mounting hardware fit perfect to the stock holes on the SMIC.