75mm Throttle Body

[Car Cannibal]

Mirage, what did you notice as soon as the shaft broke, noise, car stalling etc?

And, what about the Fords running turbo kits? I am sure some of those cars have this TB on it. Has anyone been on a mustang forum and asked if this is a reaccuring event?

 

[Hal]

You keep using the G/N as a comparison but miss the fact that those cars have automatic transmissions.

That means they hold the throttle to floor for the entire pass.

Most DSM guys lift the throttle between shifts. This means in a 1/4 mile pass a DSM throttle shaft sees 4x the abuse a G/N shaft does.

Also, the guys breaking throttle shafts on DSM's are usually running close to 30 psi (or more) of boost.

I don't believe too many Mustangs and SRT's are doing that.

You point out that the broken throttle body appears to be thin at the spot where it broke.

Again, the "half shaft" mod makes your shaft even thinner.

There's a lot of stuff on my car that's not "by the book", but it's all well thought out (I hope).

Hal

 

[Car Cannibal]

The GN's do not have a blow off. At least every time a manual gets off it the boost is getting releaved from the system and not slammed against the TB.

The bolt holes appear to be the issue here as the BBK is a full shaft yet it still busted at the thin bolt hole. The half shaft still incorporates a thicker bolt hole area, its just missing the support of the front to clamp the blade to itself.

By the way, my cars an automatic with a blow off

 

[JohnTSI]

The GN's do not have a blow off. At least every time a manual gets off it the boost is getting releaved from the system and not slammed against the TB.

The bolt holes appear to be the issue here as the BBK is a full shaft yet it still busted at the thin bolt hole. The half shaft still incorporates a thicker bolt hole area, its just missing the support of the front to clamp the blade to itself.

By the way, my cars an automatic with a blow off

Man good luck with your TB but you really do not know as much as you think you do about the pressure the TBs see. Want a broken 75mm accufab how about a 70 or you prefer a broken BBK, or perhaps a Holley? We got them all, we have a automatic and 5 speed car, the automatic sees much less TB preassure the bov is pointless until the pass is over the 5 speed cars TB see pressure 4 times on the track. They genrally have broken on the 3-4 shift with boost pressure in the 30PSI area befor the plate closed. You may have luck with you TB and I hope you do but argueing with people about GNs and turbo stangs is pointless. You know that I have spoken to SEVERAL TB manufacturers about this and been told this holds up on a GN or a mustang, guess what it didn't on a DSM. I have had a lot of luck with lighter spring in the TIAL on moving the BOV in how close it is to the throttle plate. The 70mm Accufab on the car now has need 5K without failure.

 

[Injected]

For those running the 2.25" intercooler pipes, a 62mm BBK has a diameter of about 2.45 and if you calculate the cross section including the shaft/plate assembly, you would be close to or over your flow limit. 64mm would be much better. For you guys with 2.5" intercooler pipes... I'm too lazy to do that but you get the idea. Sorry to interupt.

 

[Mirage2LTurbo]

Mirage, what did you notice as soon as the shaft broke, noise, car stalling etc?

And, what about the Fords running turbo kits? I am sure some of those cars have this TB on it. Has anyone been on a mustang forum and asked if this is a reaccuring event?

Thankfully it was a clean break, no metal parts went into my manifold. When it broke, I was on 15lbs (1 bar) going for fourth gear lift to shift. The assembly popped out of the t/b, and it locked at WOT banging off 9500rpm for a few seconds which was my set redline at the time.

 

[Car Cannibal]

John, I am making a comparison on the stock GN half shaft TB vs. the stock DSM half shaft TB. I did forget to mention until recently that I do have an auto DSM which was my base reference. If you take into account that my Talon is an auto, has a blow off and a larger TB shaft, it should do just fine like the stock half shaft GN TB without those extras. This is my arguement, that this is not going to be a cluster**ck due to the extras the DSM TB has helping it out.

My arguement with the manuals is over the stock DSM half shaft and IF it would fail. I still think that the ported stocker would hold up on both manuals and automatics. I am not convinced that a manual puts 4x the abuse ( due to shifting 4x ) on the TB than the auto's as the blow off vents off the pressure to save the shaft on every shift. I do not think the manual is solely the issue, as I bet the BBK would bust on an auto with the same turbo and psi.
Does Kiggly, Russ or any other fast auto run an aftermarket TB?
If they have busted one, than you know its the TB's for sure and the trans issue is dead.
If they have not killed one, than there is definitely much more load even with the blow off and I am wrong.

I know that the GN's use the Accufab 70mm with great luck. No BBK's or Holleys to offer any breakage info on there. But there are turbo stangs that run huge T72 turbos and have a BBK TB on it. CFM is the issue, boost psi can be deceiving as 30psi on a 14B is totally different than 15 psi on a T72. ( not saying the DSM's that are breaking the TB have 14b's )

Anyways, I would be interested in knowing the TB shaft screw size that fits the BBK's and Holleys. I think there is something to those figures worth while here.

Otherwise, I plan on making around 10whp with my ported 66mm and port matched stock intake at 25psi. IMO, this is the cheapest, easiest and safest way to get extra cfm into the DSM's right now either full shaft or half shaft.

 

[WombatTSi]

John, I am making a comparison on the stock GN half shaft TB vs. the stock DSM half shaft TB. I did forget to mention until recently that I do have an auto DSM which was my base reference. If you take into account that my Talon is an auto, has a blow off and a larger TB shaft, it should do just fine like the stock half shaft GN TB without those extras. This is my arguement, that this is not going to be a cluster**ck due to the extras the DSM TB has helping it out.

My arguement with the manuals is over the stock DSM half shaft and IF it would fail. I still think that the ported stocker would hold up on both manuals and automatics. I am not convinced that a manual puts 4x the abuse ( due to shifting 4x ) on the TB than the auto's as the blow off vents off the pressure to save the shaft on every shift. I do not think the manual is solely the issue, as I bet the BBK would bust on an auto with the same turbo and psi.
Does Kiggly, Russ or any other fast auto run an aftermarket TB?
If they have busted one, than you know its the TB's for sure and the trans issue is dead.
If they have not killed one, than there is definitely much more load even with the blow off and I am wrong.

I know that the GN's use the Accufab 70mm with great luck. No BBK's or Holleys to offer any breakage info on there. But there are turbo stangs that run huge T72 turbos and have a BBK TB on it. CFM is the issue, boost psi can be deceiving as 30psi on a 14B is totally different than 15 psi on a T72. ( not saying the DSM's that are breaking the TB have 14b's )

Anyways, I would be interested in knowing the TB shaft screw size that fits the BBK's and Holleys. I think there is something to those figures worth while here.

Otherwise, I plan on making around 10whp with my ported 66mm and port matched stock intake at 25psi. IMO, this is the cheapest, easiest and safest way to get extra cfm into the DSM's right now either full shaft or half shaft.

Yes, The Throttle body on a manual DOES see MUCH more abuse. Do you know how a BOV works? The charge SLAMS against the rapidly closed Throttle plate, then the BOV opens. The Rise in pressure in the IC piping along with the presence of vacuum in the Intake manifold is what causes the BOV to open. Its not like the BOV magicly opens as the throttle is closed, there HAS to be a large pressure differential for it to work. The BOV protects the turbo, not the TB.

In this case CFM is not the issue at all, its the force of the air hitting the Throttle plate; PSI. A 14b @30psi will stress the Throttle plate just as much as a t88 at 30psi. Sure one is flowing a hell of a lot more, but the pressure exerted is the exact same.

Also, read hals post on throttle body design, then read it again. Read it until you understand it, and why the screw size doesn't matter.