stock paxton polished kit
x-metal TB
Billy Boat stepped headers and full exhaust with cat delete
Tuner and Paxton are telling me that the increase flow of the exhaust is allowing less boost. Tuner suggested going to the 12lb pulley which would probably net me 8-9lb of boost. Anyone done this yet? And keep the stock fuel system
Ed and Donerite ...up in Wausau Wisconsin. He has done some tuning for Cory over at snakeoyl
Call Underground. (704) 361-3443 They are masters at the art of forced induction and Vipers. Kevin can tell you if what you're running is correct, and tell you where to go safely from there.
My reasoning is...if the fuel pumps that come with the stock kit can handle 8lbs of boost and I figure a 10-12lb pulley will give my car 8-9lb of boost..then I should be fine.
My reasoning is...if the fuel pumps that come with the stock kit can handle 8lbs of boost and I figure a 10-12lb pulley will give my car 8-9lb of boost..then I should be fine.
Not a safe bet. If you're using more air, then you need more fuel. If you have to spin a 12 lb pulley to get 8-9 psi, then you're moving a lot more air, hence the need for more fuel.
Don't trust psi for knowing how much air your engine is using. Psi is only a measure of resistance. An engine is an air pump. More air out = less air backup for the blower.
ILLSMOQ and I have Paxton, headers and Corsa, no cats. So theres alot of exhaust flow. We both register 8-9lbs of boost at redline. If you go with the 12lb pulley , you will probably blow your motor unless you do some serious upgrading. You really should try another tuner, dyno it, try checking boost again. Because you SHOULD be seeing 8lbs of boost.
I agree 100% - you should be getting more than 5.5 lbs. Even with the upgraded exhaust you should be getting much closer to the 8-9 its not like you have head work, cams or rockers, etc.
Make sure the belt isn't slipping, or that you don't have a leak somewhere in the piping. I would be willing to bet you will find one or the other.
Thanks fella's.... I talked to Ed this morning and stopped the order on the 12lb. He agreed that we would need more fuel so going to wait. He's going to go through everything again and see if he can find an issue.
The stock Paxton kit runs around 8lbs... if you're reading 5.5lbs something is out of whack somewhere.
"If something doesn't make sense its because one of your assumptions are wrong" - House
Quote:
Originally Posted by b3rndtt0ast
kinda like a car with ported heads will flow more at 8psi then a stock head at 8psi. but the ported one will need more fuel.
hard to explain.
Think of it in tire terms. When you put 45lbs of pressure in a 45" mud tire you have more air molecules than 45lbs in a low profile tire on an 18" wheel.
On a related note I know a guy who knows a guy that has a few CNC billet aluminum triple pump hangers for the SRT10 that could handle all of the fuel requirements for a blower Viper running 12lbs
some feedback from my tuner.....looking for any feedback I can get
Hi Josh.
I will check. I can put an optical tachometer on the blower pulley and directly measure belt slip. It is a little more difficult to measure crank pulley slip, but I can investigate it if I don’t see any belt slip. This should tell me a lot.
I check all of the vacuum lines and fittings and everything looks ok. I even te into the power brake booster line to get a better signal and the reading was the same. The pressure transducer that I use in the shop is laboratory grade instrument and is calibrat and verifi. It is ok.
If I can’t find anything then I will start to dig further. I can log inlet pressure and temperature to the blower and blower outlet temperature. This will give me the blower efficiency. With that data I can plot the points on the performance chart and see if everything looks reasonable. This will also be a good measurement of any inlet pressure drop issues.
I fairly certain it is just belt slip on top end. Check out the data. This is not the final tune and the fuel is slightly rich. You can see the boost is falling off a bit on top end.
I attach a cobra file. One plot has a centrifugal blower and the other a roots blower. The tests are from 2 different Cobras, but you can see the torque shape from the higher boost at lower RPM. This is why I suggest to crank up the boost and limit the RPM. You will gain a pile of torque at the RPM in the mid range without a bunch of stress on the engine.
Again, our altitude is 1200ft. The boost will be lower than the cars at sea level.
Thanks for all of the input. I will see if I can get is straiten out.
