psi quad question

[hontri]

Been running psi quads here in the mtns. for 10 years.I was just over in the tech section and psi reccomends 137.5 mains at sea level,and one jet size drop for avery 1500' increase in elevation.I ride at 6000',that means 4 jet sizes leaner or 127.5. Holy crap i've been running 145 and thought it ran well with good wash and plug color. What are you guys running at sea level and altitude? Any input appreciated! I can't believe i'm leaving that much hp on the table:a8:

[nate b]

if you have good wash and plug color why would you think about changing anything. unless you want to join the meltdown gang. 145 does sound a little big for the altitude, but if thats what the motor likes than thats what i'd run.

[racerrob]

Just put the PSI's on mine & run at altitudes of 4500 to 7000'
Current set up is 140's. Went out 1st time this past weekend, 30
miles on Sat in 40 degree weather & 45 miles on Tue. in 25-30 degree weather & lots of powder riding. Have not looked at the plugs yet. Will do that this weekend when I go through a few things just to check everything over. Had the heads off etc. so want to double check everything.

Yours does sound on the 'fat' side, but hey if its been working,????
:vmax4:

[hontri]

Thanks for the reply guys. Like you say if it's running good don't touch.Just curious where psi got there facts from:confused:

[Skinner]

Just pulled apart a 750 PSI perf motor, heads cut, ported, base lifted, PSI quads, about 700 ft elevation, 140 mains and the pistons are very dark (rich). Who knows how long it stays "pasted" to the bars but I guess overall the 140's look to be fat. Stay safe with the jetting, its expensive to run LEAN.

Skinner

[VMAX80096]

I run my 800 with cylinders lifted with 65 squish and airbox gutted and tops opened up 155,152.5,152.5,155....at1400ft....wouldn't go any leaner. Opening up the top does change the jetting a lot....mine are the trailblaster with the internal sliencers so from what I gather you do have to run richer but also get pipe heat way easier and faster.
With my jetting and good air with temp at 15F temps were getting to the 1300F after 3/4 run with probes 8" from the piston...was looks great. Temps scare me a bit but if the wash and plug color are fine what the heck!

[WildMax]

For stock engine internals with PSIs, at 6000' I was at 130s. Went to 135s with a Holtzman Attac and baselined for 3000' - never a problem. With major engine mods I went 2 steps richer and am on the conservative side.

To answer your concerns, I think PSI is right on for optimal jetting but I chose to run a step richer for a little protection.

[hontri]

Wildmax i was running stock internals with the quads at 6000' 145 jets,sounds like i was rich. I have since done the cylinder lift and windowed the pistons[thanks to Ken for excellent instructions] but i went a little further and took 50 thou out of the heads and rechambered them.Compression is now 135-140 with 52 thou squish. Haven't run her yet but i think i'll leave the 145's in and work from there.Thanks everyone for all the info!!! Also going to run some race fuel to start for a little security:) If anyone has any thoughts on this setup please jump in.I'm open to any ideas.:smiley-12

[IZZ]

Hontri, The 93 I bought this summer from Montana was set up for 7000' - It had psi 750 modblasters and a head cut by psi, dont know the specs but it had 160psi per cylinder, the mains were 126.3's. Now the other head was stock so it had apparently burned up one side and been put back together wrong. Thats all I know about it so take it for what its worth.