Fuel Pressure Required For Vmax 4 Turbo

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HANDSOME

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I bought this turbo max 96 st that was asphalt raced with an aerocherger running 9psi boost with stock fuel pumps. That was enough fuel for 9 seconds but I am putting it back on snow and adding an electric fuel pump after the stock pumps and a hob switch that is currently set at 3 psi.Any help would be appreciated.
 
What did your fuel pressure gauge read with stock pumps, on and off boost?

As a rule you run 10psi more fuel pressure then boost. So you should have been 9psi boost / 18psi fuel pressure.
 
Whoa... Actually the rule of thumb with boosted carb applications is 2 psi fuel pressure above boost, because the needle and seats in the carbs will not hold 10 psi fuel pressure differential and you'll find yourself chasing an overfueling / flooding gremlin and terrible drivability as a result!!!
The stock fuel pumps aren't likely to produce enough head pressure to overcome that boost level in the float bowls & probably resulted in the float bowls running dry near the end of the run. As well, they really wont flow enough fuel to feed an electric pump adaquately. I'd recommend you eliminate the stock pulse pumps all together, just run the electric. Set the base fuel pressure to 2psi at idle using a boost referenced 1:1 rising rate fuel pressure regulator (FPR) that raises the fuel pressure 1:1 with the raise in airbox pressure (boost) and dumps the extra fuel back to the tank. The boost pressure reference for the regulator should be off a nipple in the airbox close to the mouth of the carbs. This will give you more of a stock like driveability with less drastic carburetion change requirements.
Justin at FPP can hook you up with everything you need.
 
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mbarryracing said:
Whoa... Actually the rule of thumb with boosted carb applications is 2 psi fuel pressure above boost, because the needle and seats in the carbs will not hold 10 psi fuel pressure differential and you'll find yourself chasing an overfueling / flooding gremlin and terrible drivability as a result!!!
The stock fuel pumps aren't likely to produce enough head pressure to overcome that boost level in the float bowls & probably resulted in the float bowls running dry near the end of the run. As well, they really wont flow enough fuel to feed an electric pump adaquately. I'd recommend you eliminate the stock pulse pumps all together, just run the electric. Set the base fuel pressure to 2psi at idle using a boost referenced 1:1 rising rate fuel pressure regulator (FPR) that raises the fuel pressure 1:1 with the raise in airbox pressure (boost) and dumps the extra fuel back to the tank. The boost pressure reference for the regulator should be off a nipple in the airbox close to the mouth of the carbs. This will give you more of a stock like driveability with less drastic carburetion change requirements.
Justin at FPP can hook you up with everything you need.
Click to expand...

I'm a bit old school with my turbo stuff. Stock needle and seats hold 18psi. After 20psi you do switch to Grose Jets. Stock pulse pumps run in the 6psi area. Most of the old sleds didn't have the elec azz needed to power a pump 100% of the time. All the turbos I have done have no drivability issue, stock jetting, just add 100PJ and tune it. I never even put plugs in them and my 70yr old mother in law trail rides it. ;)!
 
Perfect, thanks for the replies, I have a fuel pump and regulator coming from Julien at Alpine Motorsports. Some people ask why I would buy such an ugly heavy sled. I think the v max has always been the nicest looking sled of it time. As for heavy.... thats the kind of girls I like !
 
YAMMIEGOD3:16 said:
chris, bet she is never off the throttle. LMFAO. 3:16 (yammie tony)
Click to expand...

Tony, your right. I ride the Vmax4 and always have that head light on my snow flap.

Grandma also rolls around in a Buick T-type GNX ;)!


Come to think of it, she was also the one that found that mail box with the then new 80 SRX.
 
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CHRIS I PISSED MY PANTS WHEN I READ THAT ABOUT YOUR MOTHER-IN- LAW. LMFAO. HEY YES I KNOW WEBBER WELL AND REMEMBER THAT VMAX 4. MATTER OF FACT I HAVE STOCK SUSPENSION THAT WAS IN THAT SLED BEFORE THEY WENT TO A WAHL. I USE IT IN MY 95 STOCKER FOR GRASS. 3:16 (yammie tony)
 
Ha, funny story with Webber. Back in the mid 90's I get this phone call and this guy asking all kinds of questions about using a Cat driven on a Vmax750. Then calls about a roller setup. I start asking how did you get my number? Ends up Lencco Racing was handing my number out as the yam / cat tech guy. But no one from Lencco called me to let me know what was up. Back then I'd talk to Joe about setup, then he would run Bruce Schrader (at Bender then). Bruce was working on the prototype roller back then and using Joes Lencco roller / cat as a base line. Good times! After that Joe bought Haucks (then had Jim dyno it and it was WAY off, bad deal), then a Turbo SX600.

I have not talked to Joe in years. Please tell him I said hello.
Thanks, Chris
 
i don,t know for sure but i thought that vmax 4 was used by hauck at the brainerd tar race years ago.and was not what joe bought after that. i believe latter on that sled was turned into a 800 or bigger not sure. sled was raced by mike foss after webber sold it, very fast and than tar raced. i know guy who ended up with it Try ed to run it on alcohol. i ended up with skid, tar skis, track, stock gas tank etc of it. sled today i believe is in Minnesota. chris i do know lencco performance to, mbarry is correct he has a turbo appex now. 3:16 (YAMMIE TONY)
 
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mbarryracing said:
Joe is still around. I bought the TEAM secondary off his Vmax4. Lol!
He runs a turbo Apex on the trail now, go figure. I rode his in Old Forge then I had to have one too.
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Love it! What I have found is I can make the same track hp with the bear cat driven as the TEAM. But it takes more tune time on the cat. Then it doesn't seem to adjust itself for track conditions. The TEAM seems to find peak hp for what you have that day. Cat you find peak hp at a spot and it stays at that spot for better or worse.
 
YAMMIEGOD3:16 said:
i don,t know for sure but i thought that vmax 4 was used by hauck at the brainerd tar race years ago.and was not what joe bought after that. i believe latter on that sled was turned into a 800 or bigger not sure. sled was raced by mike foss after webber sold it, very fast and than tar raced. i know guy who ended up with it Try ed to run it on alcohol. i ended up with skid, tar skis, track, stock gas tank etc of it. sled today i believe is in Minnesota. chris i do know lencco performance to, mbarry is correct he has a turbo appex now. 3:16 (YAMMIE TONY)
Click to expand...

That's what I remember too. Had to ship the motor back and raise hell. Joe was shipping it out, then putting it on Jims dyno to make sure it had real hp when it came back. It may have happen a few times before he was happy.
 
mbarryracing said:
Whoa... Actually the rule of thumb with boosted carb applications is 2 psi fuel pressure above boost, because the needle and seats in the carbs will not hold 10 psi fuel pressure differential and you'll find yourself chasing an overfueling / flooding gremlin and terrible drivability as a result!!!
The stock fuel pumps aren't likely to produce enough head pressure to overcome that boost level in the float bowls & probably resulted in the float bowls running dry near the end of the run. As well, they really wont flow enough fuel to feed an electric pump adaquately. I'd recommend you eliminate the stock pulse pumps all together, just run the electric. Set the base fuel pressure to 2psi at idle using a boost referenced 1:1 rising rate fuel pressure regulator (FPR) that raises the fuel pressure 1:1 with the raise in airbox pressure (boost) and dumps the extra fuel back to the tank. The boost pressure reference for the regulator should be off a nipple in the airbox close to the mouth of the carbs. This will give you more of a stock like driveability with less drastic carburetion change requirements.
Justin at FPP can hook you up with everything you need.
Click to expand...
Thanks for the help. I did just that. Now trying to keep battery charged.Added a voltage rectifier regulator from an apex but still not enough juice to maintain charge while pump is running.
 
HANDSOME said:
Thanks for the help. I did just that. Now trying to keep battery charged.Added a voltage rectifier regulator from an apex but still not enough juice to maintain charge while pump is running.
Click to expand...

humm I think I read that somewhere.. use to happen in the old days ;)

toydoc said:
I'm a bit old school with my turbo stuff. Stock needle and seats hold 18psi. After 20psi you do switch to Grose Jets. Stock pulse pumps run in the 6psi area. Most of the old sleds didn't have the elec azz needed to power a pump 100% of the time. All the turbos I have done have no drivability issue, stock jetting, just add 100PJ and tune it. I never even put plugs in them and my 70yr old mother in law trail rides it. ;)!
Click to expand...
 
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