Converter too tight??
Thread Starter
Joined: Nov 2009
Posts: 1,621
Likes: 31
From: THORNTON, PA (NEAR PHILLY)
Converter too tight?? Installed a PTC 9.5" converter spec'd for my combo and has the 15 stator.
On the footbrake it breaks the tires loose at ~2500-2600. I can squeak out about 5psi on the two step. I think if the converter would footbrake to 3000 I could build a lot more boost. My 245mm "low stall 2900-3000 rpm" Trans Spec unit I took out would make about 3-4psi at about the same rpm.
Should I leave this alone or have it loosened? It seems to drive nice and I would hate to have it drive looser just to be able to footbrake a little higher. Boost seems to be coming in from a roll about 500 rpm which I appreciate too.
On the footbrake it breaks the tires loose at ~2500-2600. I can squeak out about 5psi on the two step. I think if the converter would footbrake to 3000 I could build a lot more boost. My 245mm "low stall 2900-3000 rpm" Trans Spec unit I took out would make about 3-4psi at about the same rpm.
Should I leave this alone or have it loosened? It seems to drive nice and I would hate to have it drive looser just to be able to footbrake a little higher. Boost seems to be coming in from a roll about 500 rpm which I appreciate too.
Last edited by 69-chvl; Feb 1, 2015 at 07:36 AM.
What did you ask the stall speed to be set to? I called PTC to have them set a converter up for my TH400. I priced the cheaper one...and said stall speed would be around 3500rpm. I also have a transbrake and 2-step if needed, but I just assumed if ours were setup about the same then you would be able to footbrake to about 3000.
Just curious...
Just curious...
Thread Starter
Joined: Nov 2009
Posts: 1,621
Likes: 31
From: THORNTON, PA (NEAR PHILLY)
Didn't really ask, I told them the application (mostly street, anywhere from 13psi up and wanted it to drive nice which it does).
I tried all that before but was limited to about 2500-2600 b/c the tires would always break loose. I'll have to lower the limiter to 2500 now and see if any more boost can be squeezed out.
Just wondering what I'm experiencing is considered normal for the application or is it too tight. 5 psi might be enough to get a good launch anyhow.
I do think my brakes are on the weak side FWIW.
Just wondering what I'm experiencing is considered normal for the application or is it too tight. 5 psi might be enough to get a good launch anyhow.
I do think my brakes are on the weak side FWIW.
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Thread Starter
Joined: Nov 2009
Posts: 1,621
Likes: 31
From: THORNTON, PA (NEAR PHILLY)
We'll, I setup the system to dump timing to 10* and pulled some fuel and and the sucker went to about 7.5psi and spiked to 9.7 and fell back to 7.5psi. Started popping and banging like I haven't heard before. Probably could get more out of it still but how much can you really use off the line?
This was with the 2 step set at the 2600 setting.
Amazing how some guys can get 7psi w/no 2 steps/brakes, just foot brake.
This was with the 2 step set at the 2600 setting.
Amazing how some guys can get 7psi w/no 2 steps/brakes, just foot brake.
On The Tree
Joined: Sep 2012
Posts: 142
Likes: 1
From: Lehigh Valley Pa
id fiddle with your brakes see if you can get some more holding power. I know on my drum break 8.8 between crappy brakes,old master, and booster with a low vacuum cam im either pushing the front or spinning the rear and pushing the fronts
Staging Lane
Joined: Oct 2004
Posts: 89
Likes: 0
From: In the garage
What rear brakes do you have? My 15-0 would go 3600 and 8 psi with just manual master cylinder and a single caliper disc set-up. I'd agree the brakes seem weak.
I wouldn't change stall speed based on what it footbrakes. The goal of the converter is to put more power efficiently to the rear tires at WOT while still driving well and spooling fast which sounds like its doing that well. Converter changes should be made by evaluating WOT data. If you need more braking power I would address the brake system.
I wouldn't change stall speed based on what it footbrakes. The goal of the converter is to put more power efficiently to the rear tires at WOT while still driving well and spooling fast which sounds like its doing that well. Converter changes should be made by evaluating WOT data. If you need more braking power I would address the brake system.
I did a test just yesterday with my new PTC 9.5 which I believe has a 16-0 stator.
This is on jack stands, so no help from the front brakes.
I have drum rears, unknown master cylinder, and adj proportion valve for the rear brakes
Set where it was I got 2400 before the tites turned.
Turned the prop valve to give the rears full pressure and saw nearly 2900 rpm.
So yes, rear brake holding power is critical.
I plan to have my drums turned, and do the two primary shoe trick on mine. As well as pull the MC to measure the note size. If it's 1", I'll look for something smaller.
Ron
This is on jack stands, so no help from the front brakes.
I have drum rears, unknown master cylinder, and adj proportion valve for the rear brakes
Set where it was I got 2400 before the tites turned.
Turned the prop valve to give the rears full pressure and saw nearly 2900 rpm.
So yes, rear brake holding power is critical.
I plan to have my drums turned, and do the two primary shoe trick on mine. As well as pull the MC to measure the note size. If it's 1", I'll look for something smaller.
Ron
Thread Starter
Joined: Nov 2009
Posts: 1,621
Likes: 31
From: THORNTON, PA (NEAR PHILLY)
What rear brakes do you have? My 15-0 would go 3600 and 8 psi with just manual master cylinder and a single caliper disc set-up. I'd agree the brakes seem weak.
I wouldn't change stall speed based on what it footbrakes. The goal of the converter is to put more power efficiently to the rear tires at WOT while still driving well and spooling fast which sounds like its doing that well. Converter changes should be made by evaluating WOT data. If you need more braking power I would address the brake system.
I wouldn't change stall speed based on what it footbrakes. The goal of the converter is to put more power efficiently to the rear tires at WOT while still driving well and spooling fast which sounds like its doing that well. Converter changes should be made by evaluating WOT data. If you need more braking power I would address the brake system.
As long as what I'm dealing with seems OK as far as converters go I'm cool with that.
Thread Starter
Joined: Nov 2009
Posts: 1,621
Likes: 31
From: THORNTON, PA (NEAR PHILLY)
I bought my TCI transbrake for $450 I think. Installed it myself. I don't know what you would spend on a dual caliper rear setup, but $450 is not a bad price. Is there some reason you don't want a transbrake? I am not going to say it is a requirement for an auto turbo car, but it is really close to one. Helps out a ton.