Bad Cats?

[Department Of Boost]

I think I read on another forum that he had a clogged cat. Jason said that was way to much boost for that pulley size so he checked the cats.

i thought those numbers were weak for 15 lbs. definitely something going on

Yeah, 15psi is VERY HIGH for a 2.75" pulley, even on a stone stock motor with stock exhaust. That pulley has consistently made just about 12psi on a bunch of other cars.

And those numbers would be very, very low for 15psi. Depending on tune/fuel 10-12psi has been making 440-480hp.

And unless the IAT's were taken at WOT or buried in traffic they seem a bit high. With the 2.75" pulley the blower is spinning slower than a stock GT500. They stay pretty cool for a FI setup.

 

[zquez]

Yeah, 15 lbs. is definitely more than what Im supposed to have. The cats aren't bad like they were on my truck. No smell, and they seem fine. Im going to attempt a vacuum pressure test to see if there is any restriction from the cats. I had a ruptured fuel line to deal with first though... lol Problem child over here. I also wondering if its in the tune. The tuner spent most of the day trying to get my tranny part of the tune working (I did an auto to manual swap). People were backing up and Im guessing that he kinda wanted to get me out the door instead of fine tuning it. (Thats how I felt anyway) I was there from 8 till 4. Im going back next week to fine tune it. I was looking at some pictures I took of the graphs and at one point I was making more power with less boost.

In this graph I was making 455 and 476 to the wheels with 12.8 lbs of boost. But the torque curve was wavy so Im guessing thats why he kept playing with it. Its a little more comforting know that its in the tune and not something I did or something broken, if that is the case after all.

 

[zquez]

Hell, at one point I was making 466 and 497! It was doing weird stuff though. And all on less boost. With those numbers I was at 13.96 lbs. (Green line) Definitely some more tuning that needs to be done Im thinking.

 

[weather man]

Did he stop all the runs at 5,500 RPM, or is that normal for roots style blowers?

 

[zquez]

Did he stop all the runs at 5,500 RPM, or is that normal for roots style blowers?

I honestly can't tell you why he did on those runs. On my "final" run he ran it all the way to 6500. The car starts losing horsepower @ around 6000 rpm and torque at 4500.

 

[Department Of Boost]

Did he stop all the runs at 5,500 RPM, or is that normal for roots style blowers?

With stock bottom ends I wouldn’t run it past 6K. There’s no point. It’s making peak power a lot sooner than that.

 

[lito]

IAT's were monitored during those runs? Have you related both?

 

[zquez]

Im sure the IATs were monitired but I dont have the data. When I go back next week, Im gonna get as much info as he'll give me. I think that the high IATs were recorded on a back to back run on the dyno. So that might explain why they were so high in the first place. The tuner mentioned that the IATs shoot up 50 degrees or so during WOT and that when he sees that it usually means the intercooler cant handle it or some shit.

 

[Department Of Boost]

The tuner mentioned that the IATs shoot up 50 degrees or so during WOT and that when he sees that it usually means the intercooler cant handle it or some shit.

Well I can say with 100% confidence it is not the intercooler that is underperforming. If anything is underperforming at all it is the pump or heat exchanger….or both.

 

[lito]

Very high IATs will go inline with higher boost reads, the hotter it gets the higher the pressure.

 

[zquez]

Well, I was gonna hook my tuner up to the car to do some datalogging. I had to update the firmware though. During the update the damn thing froze. Now I dont have my dyno tune, and the car was set back to stock. Fuck me. Hopefully my tuner is in town and can email me the damn thing. I swear theres always something....

 

[lito]

Pretty sure the tunes are still there, if SCT takes too long to respond, using an older forced firmware replacement and then do the update sometimes help

 

[908ssp]

Mine makes 450 at 12lbs with a 2.75" pulley. And runs around 115 degrees IATs with 90 degree ambient temp while driving in traffic.

Have your tuner check the tune for the stumble.

 

[zquez]

Mine makes 450 at 12lbs with a 2.75" pulley. And runs around 115 degrees IATs with 90 degree ambient temp while driving in traffic.

Have your tuner check the tune for the stumble.

This is my final dyno pull.

 

[JeremyH]

Yeah that torque curve isnt right, tq is just dropping off hard, somethings not right imho....

 

[zquez]

When I look closer at the boost graph it only seems to peak at 14.77 at the very beginning of the pull right around 3k rpm. Then it settles down around 12 or 13. Is that even something to be concerned about? I guess it only takes the pressure to be high enough for a second to break stuff though... Can't wait till next Tuesday so I can get this all sorted out

 

[Department Of Boost]

Yeah that torque curve isnt right, tq is just dropping off hard, somethings not right imho....

Agree, something is not right.

The boost is doing something funny

The torque curve looks strange

And I have yet to see one make more TQ than HP

 

[zquez]

Could a small intercooler leak cause a boost spike like on the graph at 2900 rpm? One of the fittings on the back of the manifold is a little loose. It leaves about a 2 inch diameter pool on the floor overnight . Coolant levels are still in check. Or maybe a vacuum leak at the blower elbow? As far as I know I don't have a vacuum leak but Im just throwing ideas out there.

 

[JeremyH]

Rise in boost would be the ooposite, would identify a restriction in flow somewhere forcing pressure up.