8k+ you're good at 9 
Sea level, even 7 you're flirting with taking out your bearings. Every sled is different as far as fuel system, the most consistent I've seen is a little under 9 at sea level. But at that you need good fuel. If you push the limits your rod bearings are typically the first to see it and if you don't catch it knocking you will send a rod through the block.
Dime, with how many miles you have and at 9 @ 4k I wouldn't be surprised if deto didn't have a part in your bearing failure.
Think of it this way, the engine is roughly a 11.5 to 1 compression. @ 7.4 psi @ sea level were forcing 50 percent more air into the engine. Now it is acting as a 17.5 to 1 compression engine. How many people would run a 17 to 1 engine on pump gas? These are all rough figures but you get the point.
I was resistant to a lower compression engine for a season, after a lot of seat time on a engine with a .060" head shim I don't really see a reason not to do it anymore. It's still a Nytro with a ton of low end power, but its safe.
Sea level, even 7 you're flirting with taking out your bearings. Every sled is different as far as fuel system, the most consistent I've seen is a little under 9 at sea level. But at that you need good fuel. If you push the limits your rod bearings are typically the first to see it and if you don't catch it knocking you will send a rod through the block.
Dime, with how many miles you have and at 9 @ 4k I wouldn't be surprised if deto didn't have a part in your bearing failure.
Think of it this way, the engine is roughly a 11.5 to 1 compression. @ 7.4 psi @ sea level were forcing 50 percent more air into the engine. Now it is acting as a 17.5 to 1 compression engine. How many people would run a 17 to 1 engine on pump gas? These are all rough figures but you get the point.
I was resistant to a lower compression engine for a season, after a lot of seat time on a engine with a .060" head shim I don't really see a reason not to do it anymore. It's still a Nytro with a ton of low end power, but its safe.
Dimebag said:
I do/have 10psi at sea level.
I was thinking I had a video of it that would show my AFR gauge but all my videos I have are from out west.
I'm thinking I turn it down a bit as most of my riding has been with my wife and a stock nytro is more then enough when riding with her let alone boosted.
But when I'm with the guys or out on the lakes 10 is sure fun. Then I will just fill up with Av gas.
Scary part about this is I was only running 6 pounds here and Ken from Push said the motors can handle 10 at sea level.
17:1 heck we could run diesel thru them.
kidding of course.Mike
Dimebag
TY 4 Stroke God
- Joined
- Nov 3, 2009
- Messages
- 1,777
- Reaction score
- 10
- Points
- 483
- Location
- Norway, 68N
- Website
- www.ty4stroke.com
Yep. That might very well be true.
But how are the push kits able to run 8 psi at sealevel producing 200 hp?
Or even 10 psi @ 225 hp? At least thats what they advertise.
Im running the n/a xtx while waiting for new bulkheads for the turbo.
Wow, its a different world without the turbo..
But how are the push kits able to run 8 psi at sealevel producing 200 hp?
Or even 10 psi @ 225 hp? At least thats what they advertise.
Im running the n/a xtx while waiting for new bulkheads for the turbo.
Wow, its a different world without the turbo..
I have wondered the same thing.
It would be nice to see a dyno graph to see how flat the HP is or does it just spike.
It would be nice to see a dyno graph to see how flat the HP is or does it just spike.
Dimebag
TY 4 Stroke God
- Joined
- Nov 3, 2009
- Messages
- 1,777
- Reaction score
- 10
- Points
- 483
- Location
- Norway, 68N
- Website
- www.ty4stroke.com
Yeah, i saw that.. I was wondering cause i was considering to buy a push kit for the xtx.. But i believe i have decided to keep it stock.
Ouch. I think I will turn my down. I'm thinking the Av gas might have saved my butt.
And idea if he was running a AFR gauge?
And idea if he was running a AFR gauge?
Dimebag said:
Head shim it and run a OFT equipped push kit
I wouldn't hold that against push, I don't agree with the published boost numbers but that can be set where the user desires.
- Joined
- Apr 17, 2003
- Messages
- 5,541
- Reaction score
- 1,402
- Points
- 2,003
- Location
- Menno, SD
- Website
- www.ulmerracing.com
- Country
- USA
- Snowmobile
- 2014 Yamaha SR Viper LTX, 2014 Yamaha SR Viper RTX SE, 2015 Yamaha SR Viper MTX SE 162 (turbo), 2015 Yamaha SR Viper MTX SE 153
- LOCATION
- Menno, SD
- WEBSITE
- www.ulmerracing.com
In the last 2 weeks I have had 5 phone calls from Push owners that have hurt their motors. All with less than 500 miles on them at sea level.
If you're running pump gas on the stock fuel pump/regulator setup on a FX Nytro I would stop at about 6 psi of boost.
If you're running a aftermarket fuel pump & regulator and have a decent fuel controller then you can run 7.5 to 8.
If you have a thicker head gasket (0.066" total thickness) then you can run 10-11 on pump gas (again only with a good aftermarket fuel pump & regulator and a decent fuel controller).
If you're running pump gas on the stock fuel pump/regulator setup on a FX Nytro I would stop at about 6 psi of boost.
If you're running a aftermarket fuel pump & regulator and have a decent fuel controller then you can run 7.5 to 8.
If you have a thicker head gasket (0.066" total thickness) then you can run 10-11 on pump gas (again only with a good aftermarket fuel pump & regulator and a decent fuel controller).
Srxspec said:
Well said Allen
Hopefully Push goes back in changes his suggested numbers.
They seemed high but he also seemed rather certain you could run those numbers.
Guess I will be pulling the plugs tonight and checking with a bore a scope to make sure I havent done damage.
I'm thinking the Ava gas saved me here.
They seemed high but he also seemed rather certain you could run those numbers.
Guess I will be pulling the plugs tonight and checking with a bore a scope to make sure I havent done damage.
I'm thinking the Ava gas saved me here.
fxnytroxtx
Guest
Srxspec said:
Almost 3k boosted 3500 total miles on mine with 10:1 pistons fuel pump and regulator 10-12lbs no extra cooling a lot of lakes and runs like a champ.
This season I reflashed my ecu timing and water fix. They say shold be able to run 2-3 lbs more. Didn't try turning up boost because my a/f sensor is toast.
boost
I think push is pushing his boost recommendations. I have a MPI turbo kit and I have it set up to run at 5.5lb of boost and I am seeing AF of 11-11.5 at wide open. I know its a little rich but some times I don't always have the perfect water temps. Im tying to play it safe.
I think push is pushing his boost recommendations. I have a MPI turbo kit and I have it set up to run at 5.5lb of boost and I am seeing AF of 11-11.5 at wide open. I know its a little rich but some times I don't always have the perfect water temps. Im tying to play it safe.
Dimebag
TY 4 Stroke God
- Joined
- Nov 3, 2009
- Messages
- 1,777
- Reaction score
- 10
- Points
- 483
- Location
- Norway, 68N
- Website
- www.ty4stroke.com
Srxspec said:
Do you mean that running 7 psi at sealevel like the mcx 190 setup is not safe?
Isn't he 240 kit still running the stock fuel pump?
Thanks
tjc
Expert
Maybe I will just muddy the water but I think you will find he is giving a rule of thumb, from his experiences. You will find every sled is a bit different and each manufacturer will put out what they feel are safe numbers with their kit.
6 pounds is not really 6 pounds across the board. Intercoolers, fuel systems, and turbo selection will all play a part too.
6 pounds is not really 6 pounds across the board. Intercoolers, fuel systems, and turbo selection will all play a part too.
