Confused about boost numbers on pump gas

[KJFarmer]

After reading on here for awhile and looking at all the Nytro turbo kits available, i have come to the conclusion that i am lost!

Just wondering about what boost i can run on pump gas at elevation like 6000 and above, a lot of the talk on here sounds like 10-12 sounds about max (not sure if that is with or without a shim) Heard the mcx 270 kit is pump gas and figured that would be about 13lbs of boost if im right??? Also Impulse claims 17lbs of boost at 5000ft and above on 91. Thats the number that confuses me, how can they run so much more and be safe when everyone else seems to say right around 12 would be max.

Just hoping someone could get me straightened out on this and less confused, Sort of new to the Yamaha turbo scene as i just sold my M8 and bought a 2010 Se. Dont really feel like messing with race gas a whole lot as i did it on my M8 and it just got to be a hassle to having to make sure you got enough and worrying about it.

Thanks for the info in advance. Please dont get on me too much about being cheap on race gas and having a 20,000 sled. haha its more of a availability issue more than anything

 

[BigFish BC]

the impulse at 17lbs pump gas has a shim & timing to make 17lbs a pump gas kit. same as the mcx 270 kit has a shim & controler.most true pump gas kits no timing or shim 8-10lbs boost is max around 200-220hp.this is just a simplified explanation there is allot to it & it takes a bit to figure it out, there is allot of thing that help make more or less boost safe

 

[Wheel House Motorsports]

it depends a LOT on the motor work done.

I cant speak much for the nytro's as most of my knowledge stems from the 4 cylinder yami motors. BUT, the reason some can do different levels is 2 things, head shim thickness, and other part efficiencies.

Impulse runs a thick shim and because of the standalone system they can tune em nice and safe at those levels with proper fuel level and timing taken out, this is what is allowing you to push it farther on pump 91. another big factor is the efficincies of parts. the impulse can move a LOT of air and keep it cold going into the motor, so can mcx due to the rear mount and effectively double intercooling, so your charge temps are cooler, thus less likely to detonate on a certain fuel.

as far as race gas, IMO, running a shimmed yami motor, its gonna do more with 91 then most people ever are gonna need. Any of the larger kits available on pump fuel will go places nobody needs to be day in and day out.

 

[KJFarmer]

From the guys i ride with, which are mostly lightly modded m8s and a proRMK, I figured 12lbs of boost would be enough to do what we usually ride, but i do like the fact of knowing i can turn it up to 17lbs safely everyonce in awhile for the big pulls and not have to worry about det. Also how much does the bigger shim in a impulse kit hurt the bottom end when playing in the trees and boondocking? I would like to stay with a front mount turbo just because i hear and figure the short header would keep the lag down and just like the look of there kit. Seems like theres quite a few of them out running around.

Sorry if it seems like this may have been beat to death on the forums but ive read as much as could find and still have questions to answer if you dont mind.

 

[irondave86]

The impulse nytro I rode had the 9:1 shim and the bigger 3071 turbo, and it was pretty responsive. Between the placement of the turbo and proper clutching lag is very minimal, and the bottom end power was still very usable. It's defiantly a well put together kit.

 

[ROBERTSONYAMAHA]

On the Mcx Kits we are running the following on 91 Oct. Pump Fuel and this is what is recommended by MCXpress.

MCX-180HP Nytro - No Head shim - 6-9lbs. Boost
MCX-240HP Nytro - Head shim - Intercooler/Injectors etc - 12-15lbs. B
MCX-270HP Nytro - Head shim - I.Cooler/Injectors/Fuel Pump - 16-19lbs.B
All on pump fuel

310HP kits and up are a 50/50 mix. 270 and under are pump fuel.
Anymore questions PM me.

 

[Zipperno]

The Impulse standalone kit uses a .080 shim and two stock gaskets. Superlow CR around 8.25:1. Because of the midmount turbo it has no lag and is responsive

 

[KJFarmer]

Sounds like the impulse kit is the way to go for what im wanting, has anyone had any issues or problems with the kit, and the standalone that i keep hearing about is that included in the non racing kit?

 

[Ak nitro]

This is my fourth season on my Impulse and it has been a lot of fun, the standalone is standard now on all kits. It is very nice to not have to deal with those adjustable boxes anymore. I still have a o2 sensor on my prologger, but I never check the A/f ratio anymore because it is always dead on. If you are looking for the least amount of lag possible than Impulse for sure.

 

[800tundra]

Have mcx 270 kit running av gas around 2200 ft for safety when riding around home Installed manual boost controller so I cod run it at 12-14 lbs boost and premium but didn't seem to work to good to due having it clutched for runnin at 17lbs. that's even with whith adjusting shockwave. So now it stays at 17.Something to keep in mind

 

[KJFarmer]

Did you adjust the primary at all when turning it down to 12-14lbs?

 

[philsummers21]

I was like you that wanted to run 17lbs if i needed to. Problem is you can't go from 12# to 17# and not change your clutching. set it at 14# and ride. You'll be able to do just about everything you ever needed to.

 

[KJFarmer]

Understand the clutching holding a guy back from changing boost on the fly so to speak, just wanted to make sure i understood what kind of boost i could run while still running pump gas

 

[summitboy]

From another post(I Included it all):

Yes T-Birds theory is sound and this is how MCX explains the numbers as well. However what is safe on pump in Sweden may or may not be safe here in Canada/USA. I say this because the fuel is different from there to here.

I ran the 16T forever on pump at 12psi (6000-7000ft) i know a guy would be safe to 14psi for sure. Here in Canada when guys were running the 310 kit with the 16T they were running 17psi on straight Avgas. Can it be done on straight pump ?? I don't feel like being the test dummy. As NM said running a 50/50 mix is smart insurance but may or may not be for everyone cost or practical wise.

I understand the Nytro MCX 270 is set at 16 psi at sea level and then auto compensates at altitude. I know certain individuals can chime in and tell us they see 17-19 psi (auto comp) at the 6500-7000 foot mark all on pump premium. What these motors can take for max boost in all conditions on pump is a guessing game.

Running the auto compensate on the MCX say on the Apex 290 kit, hitting the 17-17.5 psi at altitude (6500) on pump may be pushing it in my opinion especially if your fuel is not top notch, which can supposedly happen. I'm no expert, just trying to come up with a good safe number to stay on pump premium. MCX says you need 200KPA total/absolute pressure for 290 pump. at 6500 feet you have 80KPA, you then need 120 KPA to make your 290 which is roughly 17.5 psi supposedly safe on pump. Who's pump ????

Air/Fuel may not necessarily tell you your in deto land. This is MCX head shim of course. Low compression pistons would change things especially if compression is lower than the head shim which i believe it is, but not 100%. Just some food for thought.

Some numbers for thought

Apex 16T 260 HP (180 KPA)
Sea 12 psi
6500 14.5 psi

Apex 19T 290 HP (200 KPA)
Sea 14.5 psi
6500 17.4 psi

Nytro 16T 180 HP (140 KPA)
Sea 6 psi
6500 8.7 psi

Nytro 16T 240 HP (190 KPA)
Sea 13 psi
6500 15.9 psi

Nytro 19T 270 HP (210 KPA)
Sea 15.9 psi
6500 18.9 psi

Keep in mind these are a little rounded and using 100KPA sea and 80KPA 6500.

 

[robb]

boost

My 270 MCX will run 16lbs of boost at 1700ft elv. Then in revy it runs 18 lbs of boost at 7000ft all on 91 pump prem. This year i bought some VP C111 and add about 25% but i dont think i needs it. "Just to many guys gave me the the big scare that it needs more then 91 prem ?

 

[astro]

I played around with a knock sensor last season. Running at 225 kpa on 91 I had to add about 8 degrees of timing before I started picking up detonation. This was in my sled with the Seadoo RXP motor. I learned that with lower compression (8.5 in my motor) and some timing pulled out you can run a lot of boost before it knocks. Pushing it right to the edge with timing didn't really add to the riding experience, as it is I hardly ever use more than 60% thottle. Seems like anti-lag would be a better place to put your effort so the power was on more in the low Rs

You are wondering which kit to go with? Just remember you probably won't use that max Hp all that much. I'm in the 350 range and it is just kind of ridicules. Never had a situation where I've had to hold it anywhere close to pinned. Most of the time I'm not above a 160-170 kpa and still going up the hill way faster than I should

 

[KJFarmer]

Main reason i wanted to know which kit and how much boost i could run on pump gas was to know i wouldnt be running on the edge. I'd like to be in that 12-15lb range on pump gas. So the way it looks ill be running an impulse kit that is rated up to 17lbs on pump and only running it inbetween 12-15lbs, that way i know if i get down a little lower in elevation than expected its not gonna knock and its not right on the edge of detnation, if that theory sounds right at all idk, im still learning

 

[XtremeSpeedShop]

Turbo leg with the Impulse kit is close to non existent as you can get for a turbo. Not to mention the standard kit can be turned down for pump fuel or cranked up to run with the big dogs. No box to change maps and have to be worried if its spot on. Just gas and go! If your worried about throttle response watch this and hear how quick the motor gets on and off boost...

http://www.youtube.com/watch?v=DiXsWZrUG6M