Setup Wont build boost on footbrake or 2 step. Ideas?
Setup Wont build boost on footbrake or 2 step. Ideas? Im new to the boost thing and have almost completed my first project. Car drives well and hits full boost (8lb gate pressure) by 3500rpm. Car is a 383 LT1 TH400 billet S480 T6 226/226 cam.
I am not a not a converter guy but I have a 3k stall converter (local built custom converter) and when I try to footbrake it, it builds zero boost. Then i tried the same thing with my transbrake and upped it to 3500 rpm for 3 or 4 seconds and zero boost was built.
I dont have any boost leaks but I was wondering am I not building boost because my 2 step is not installed? Maybe it takes WOT to build boost and the 2 step would help. I thought at least by foot braking and tbraking it, it would at least build a couple pounds.
Do yall have any idea on why is this an issue? Does it sound like the converter is too tight? 2 step installation needed?
I am not a not a converter guy but I have a 3k stall converter (local built custom converter) and when I try to footbrake it, it builds zero boost. Then i tried the same thing with my transbrake and upped it to 3500 rpm for 3 or 4 seconds and zero boost was built.
I dont have any boost leaks but I was wondering am I not building boost because my 2 step is not installed? Maybe it takes WOT to build boost and the 2 step would help. I thought at least by foot braking and tbraking it, it would at least build a couple pounds.
Do yall have any idea on why is this an issue? Does it sound like the converter is too tight? 2 step installation needed?
Check out the first 20 seconds of this video. This just so happens to be a cast s480 turbo also. The first time I rev the car is with the 2 step DISABLED and only using the transbrake. As you can see, there is a ton of load, and the car goes to make gobs of boost and push through the converter instantly. Then the next time I rev it, is with the 2 step ACTIVATED and you can hear that it makes a steady amount of boost just fine.
If I had to guess what was up with your system, I would think that maybe you either have a leak in the system (Hot side) or that your wastegates open way too early and don't allow your exhaust to build the pressure to drive the turbo.
If I had to guess what was up with your system, I would think that maybe you either have a leak in the system (Hot side) or that your wastegates open way too early and don't allow your exhaust to build the pressure to drive the turbo.
Thanks for the input. Im leaning towards the wastegates are opening too soon idea. But it baffles me that when Im datalogging and go WOT it hits boost fine and makes a total of 7.69lbs pretty consistent. So why would it be different when stalling up?
Im not following you on this. I thought at least footbraking would net a couple pounds. I thought I should bring up the Rs up for at least 3-5 secs and then see at least 1-4lbs of boost.....
Does the car have a blowoff that is plumbed to the intake? If it does, it wont build boost until WOT. Put it on the transbrake at wot as this is how its supposed to be used. Even without the two step it will only go as high as the stall of the converter so there is no need to be at part throttle.
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I finally figured it out. I wasnt making positive boost until 4037rpm via my data logger. So I stalled car up on footbrake to 3000 and then from 3000-4000 on the brake it made boost. Didnt even have to go WOT. So I will remove converter and get it restalled for about 4000 this time around. The car felt and sounded like it was prepared for take off!
I finally figured it out. I wasnt making positive boost until 4037rpm via my data logger. So I stalled car up on footbrake to 3000 and then from 3000-4000 on the brake it made boost. Didnt even have to go WOT. So I will remove converter and get it restalled for about 4000 this time around. The car felt and sounded like it was prepared for take off!
don't be to fast to up the stall just yet. you don't want that converter to slip to 4000 or you will blow right thru it when in boost. if it hits boost by 4000 without a 2 step it will make boost at 32-3400 on the 2 step when floored.
if what your telling me is it makes boost on the trans break at 4000 that's good. you need the load to produce heat in the exaust to get it spooling. and a t break plus 2 step at 3400 or so should get you close to a decent launch and you can adjust the 2 step from there for the desired launch /boost.
at 10 #boost I bet your current converter will be near 5000 and that's not to far off to start.
if what your telling me is it makes boost on the trans break at 4000 that's good. you need the load to produce heat in the exaust to get it spooling. and a t break plus 2 step at 3400 or so should get you close to a decent launch and you can adjust the 2 step from there for the desired launch /boost.
at 10 #boost I bet your current converter will be near 5000 and that's not to far off to start.
don't be to fast to up the stall just yet. you don't want that converter to slip to 4000 or you will blow right thru it when in boost. if it hits boost by 4000 without a 2 step it will make boost at 32-3400 on the 2 step when floored.
if what your telling me is it makes boost on the trans break at 4000 that's good. you need the load to produce heat in the exaust to get it spooling. and a t break plus 2 step at 3400 or so should get you close to a decent launch and you can adjust the 2 step from there for the desired launch /boost.
at 10 #boost I bet your current converter will be near 5000 and that's not to far off to start.
if what your telling me is it makes boost on the trans break at 4000 that's good. you need the load to produce heat in the exaust to get it spooling. and a t break plus 2 step at 3400 or so should get you close to a decent launch and you can adjust the 2 step from there for the desired launch /boost.
at 10 #boost I bet your current converter will be near 5000 and that's not to far off to start.
My converter only stalls to 2500 rpm on the t brake and I can still manage as much boost as I want playing with the tune. It just takes a while. If your converter gets to 4000 rpm before boost its already too loose.
What I thought was the best it could be
What I ended up with after trying many different tune strategies.
What I thought was the best it could be
What I ended up with after trying many different tune strategies.
don't be to fast to up the stall just yet. you don't want that converter to slip to 4000 or you will blow right thru it when in boost. if it hits boost by 4000 without a 2 step it will make boost at 32-3400 on the 2 step when floored.
if what your telling me is it makes boost on the trans break at 4000 that's good. you need the load to produce heat in the exaust to get it spooling. and a t break plus 2 step at 3400 or so should get you close to a decent launch and you can adjust the 2 step from there for the desired launch /boost.
at 10 #boost I bet your current converter will be near 5000 and that's not to far off to start.
if what your telling me is it makes boost on the trans break at 4000 that's good. you need the load to produce heat in the exaust to get it spooling. and a t break plus 2 step at 3400 or so should get you close to a decent launch and you can adjust the 2 step from there for the desired launch /boost.
at 10 #boost I bet your current converter will be near 5000 and that's not to far off to start.
I agree with yenkomike. I would get it tuned properly on the brake and two step at wide open throttle and see where its at. Boost or nitrous makes a big difference on stall. I had a 68 camaro pro charger big block that would only stall 3000 RPMs with the belt off it on the transbrake. On the transbrake with just boost it was at 5000 and on boost with a 250 shot it was 6000 on the brake. Point being if the tune or timing is not optimal or your not at wot on the trans brake with the two step then you really have no idea where the stall is going to be or how much boost you can make on the leave. Still not sure why your not testing this at wot...it needs to be wide open there's no point in knowing it makes boost at part throttle as that's not how you should be leaving with it.
Yes, the 2-step will help out a lot. I don't have a transbrake and can barely make positive pressure without the 2-step engaged. With the 2-step set at 3400 I can make 8-9 lbs. and cut high 1.3 60's off the footbrake.
So I have come to the conclusion that the converter that I currently have may be a pretty close fit to what I need. I just need that 2 step installed and some fine tuning.
What 2 step did you use and what adjusts did you make to the tune to make it all work? Just curious...
What is your gate pressure set at? Mine is 8#. I am wondering if I could make 8# on the brake
The rpms at wot on the transbrake will only go to the stall of the converter so you wont be over revving the engine at all. The two step will allow you to lower the rpms to a point lower than the stall of the converter. Also I asked in an earlier post if you had a blow off. If the blow off is plumbed to a vacuum source (on the intake side of the throttle body) this will cause a huge boost leak until you get to wot and/or overcome that leak to build boost. If you disconnect the vacuum line from the blow off you may be able to build boost easier for part throttle testing.