Re: Who says a .68 exhaust housing is too small? *Update: Videos!

I hope to be doing that soon if I ever get off my rear. Very nice job on her. What brand exhaust are u running on it? Sounds awesome.

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

Log files we have. MP T70

302 - 15psi =.68 @6000 was 41 BP
.81 A/R@6000 = 37
.96 A/R@6000 = 32

Tried 17psi, and now we have the unit here with a broke shaft....hehe.


Food for thought.......

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

so you are implying that the turbo will break if run over 16psi due to back pressure in the exhaust (pre-turbo)?

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

No, we have units that have gone over that, but we are seeing shaft vibration problems with some of the MP units. We think its the shaft diameter is a touch small for big boost. But this has only been an issue on the smaller cube engines that see 25-30+ psi.

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

I think some people are missing the point. He's saying that the .68 housing is perfect for his application and for others who are using stock shortblocks, or stock blocks. So let's say he gets a .96 housing and turns it up to 25psi, well he'll blow his block apart. If he switches to a .96 housing in order to reduce backpressure than he'll have a laggy turd, and it will be boring to drive and won't be as responsive. So would some of you consider a stock shortblock car that has been abused it's whole life, with old heads, a non turbo cam, that is driven everywhere, and runs 10.50's at 130+ all day long a failure just because he has 15 more psi backpressure than a .96 housing?

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

Do the calculations first then post. 15psi of backpressure on a 550-600hp engine at the crank can be worth 50-60hp difference. Also with a 302, a T70 is not going to be laggy with a .96A/R....its still a 302ci engine . Heck we run them on 3.0L 2JZ's with limited lag.....lol.

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

Lol, its not going to blow up but it would breathe better with a larger A/R and free up some more power.


You you know what your EGT's are?

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

Isn't the general rule of thumb that you want your max BP to be roughly 2x the boost pressure? i.e. the .96 looks like the ticket for max performance, but obviously the low end would suffer as compared to the .68...

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

a .81 would probably free up some hp on this car, but at the same time, freeing up 50-60 hp (if it actually did that w/ a direct switch) would probably be enough to split the block. And if JZ said they didn't experience the damage problems until 25-30 psi anyway, then what's the worry if this one's not gonna see much more than 13 w/ the stock block? Why spend the money to upgrade when the boost response is comparable to a roots blower? I should get video of his boost gauge, it's hilarious!

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

i think it's great his car is running like it is. i run a .81 on my MPT70 and love the response. i was just questioning the statement that someone had shaft breakage with 17psi. turns out 25-30psi becomes a problem, but as i never plan to run that much on my stock bottom end 302 i have no worries

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

Fking Sweet!

If that thing runs a 10.4 or 10.5 @ whatever mph with the smaller housing on slicks I'm gonna fall out of my chair. Have you any thought on trying a before / after .81 test with a pair of tires that hook

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

I like my 0.68 A/R better than the 0.81 A/R I had on previously. Spool occurs ~300 RPMs sooner, which for a mostly street car = a meatier torque curve and more fun.

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

Hey darin, it's Mike Beemer from Wichita, Ks. I ordered a 4" - 3.5" silicon reducer that I used on this setup. Just wanted to say thanks, it worked great!

Maybe the .68 is costing me some power, but I'm not trying to make all out maximum power here. I have absolutely fantastic boost response with this housing, and obviously it's making good power, otherwise it wouldn't have went 130+ mph like it did. I think that if I were to bolt on a set of 28" tall slicks that the car would mph even higher. For one, I would stay off the rev limiter on the big end, and having traction all the way from the starting line to the finish line would surely pick up mph too.

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

Sweet, that's what I want to hear. I've got a .68 housing too and was worrying about what my limit was. Got a stock shortblock too hoping for the 10's, gone 11.46 so far. Getting there.

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

Nice times!!!
When you say dirt tires do you mean Hoosier dirt bosses??? I ran those for awhile and they worked pretty darn good.

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

Nice #'s....

I am running the MPT70 w/ the .68 housing also on a 306 with an AOD. I have gone 10.68 @ 129 w/ 10psi and pump 91.

I have now bumped the boost up to 14, and am using water injection with pump gas. I hope to go out and run the car this weekend, and i will post the results.....

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

very impressive...

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

amen, that is a runner right there....man

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

nice times man...

 

Re: Who says a .68 exhaust housing is too small? *Update: Videos!

Excellent .(Mr. Burns voice) ( touching fingers together)