desperado

Great opinions and outstanding discussions right here. 100% agree about safety requirements.

I also fully agree the 1200 internals are built tough and can take a lot of abuse. However, we are in the business of setting up engines that successfully and safely operate at boost pressure well beyond 38-40psi which is what many people see as overboost. Our engines are now routinely operated at 48-50psi and we have yet to see one single failure after 2 full race seasons with several sleds. I am not saying we'll never see a blown engine, I am sure we will one day. All I am saying is that we aim at engineering our designs with the required safety factors that are typical of world class motorsports race applications -- therefore, fully forged and balanced internals are a no brainer in this context. The nice thing about building engines that resist the test of time and the extreme conditions in which they are raced is the fact we dissassemble them after each season and we measure and inspect every component. This provides a wealth of information about where the true limiters are and we work at improving on those on an ongoing basis. I hope this makes sense.

Interesting. Here is my perspective for what it's worth.

Bike applications require good transient rpm throttle response and twin injector per cylinder often make sense in those applications. However, full drag race snowmobile applications using a CVT do not require sophisticated transient rpm fueling strategies. In fact, what defines if transient rpm is efficient is "time to full spool/boost pressure and peak rpm". An efficient setup should allow to go from launch rpm and boost pressure (say 4500rpm and 8psi on the antilag) to peak rpm and boost(say around 8800rpm and 35psi) within less than 0,6 seconds. This means transient rpm lasts less than 0.5 second and beyond this timeframe, the injectors are already flowing over 1300cc per minute, therefore the need for twin injectors per cylinders isn't justified in that operating condition. A key challenge with large single high flow injectors (beyond 1500cc per minute) is fuel distribution at low duty cycle. Good tunes will always incorporate smart strategies to deal with situations when injection time are low enough that injectors require to be synched with intake valve opening to avoid fuel puddling in the intake tract. Another challenge is fuel atomization and droplet size -- not much can be done here, except ensure that only best quality injectors are used.

Totally agree on the current F1 injector placement and the related benefit. However, these setups are for totally different applications running naturally aspirated engines at much higher rpm (read intake tract velocity and pulse width), highly varying rpm and torque bands and sky high fuel pressure to maximize fuel vaporization.

Just to show what Bluemax was talking about, here is an example of F1 injectors placed at the intake tract entrance, As you will see, transient rpm efficiency is what is being tested on the dyno.

Very sorry for the misunderstanding.

When I mentionned QRS, I meant with the jackshaft -- in true factory terms. And yes I agree, composite fuel components are more fragile than aluminum, especially when fuel hoses are poorly routed and binding.

Having said the above... we always rework what we feel can become a weak link, just like anyone else on here.... so, it would be a mistake to assume the QRS or fuel rail systems we use are setup 100% as per the oem configuration.

My other black turbo sled described in "MY Turbo Build" on Dootalk is staying the same for trail duty with the exception of a custom exhaust cutout using a tial MVS 44mm wastegate activitated by boost pressure to decrease downpipe backpressure while under higher boost while keeping trail friendly quiet exhaust.  It is also getting a custom cut larger top gear to maintain reverse while eliminating chain failure issues due to the small contact area on stock gear. 

This is the system Brian is talking about.... ran it all year, best of both worlds: quiet when cruising and less restriction when WOT + roaring sound when the flipper is pressed to the bars.

 

 Exhaust 1.jpg   35.13K   38 downloads

 

 exhaust 2.jpg   21.67K   34 downloads

 

Looking good Brian, I have a question , what are you using for a fuel rail, stock or did you source something out.

We have had no issues feeding the 2200cc injectors at up to 70% duty cycle with the oem fuel rail. Fuel pump volume to support the required combined flow at the required 85psi fuel pressure is where the challenge is.

 

that stock jack shaft will not support any where near 600hp

it may work without any traction but if your hooked (no spin) there is no way

We have not experienced issues with the QRS as you suggest Chris. We have broken chains and completely sheared track shafts, but no QRS failures.... yet. I am not suggesting there isn't anything better on the market, I am just saying the QRS has been reliabe in our case.

 

Another neat feature which I am hoping to have incorporated in the sled is a single axis yaw control sensor which will feed the motec data giving gyroscopic contol over wheelies and will automatically pull timing while maintaining boost to bring the front end down in milliseconds and restore power in milliseconds with no lag. This will enable the driver to stay in the throttle and not have the devastating effects of loosing boost and suffering turbo lag from the large turbo if having to get off the throttle to bring the front end down.  Letting off the throttle would ultimately send you to the trailer in a race because by the time boost is restored after hitting the throttle again, the race will already be lost.

You are right Brian... there is no 2nd chance with a large GTX3582R... let off the throttle once, even if very briefly, and the race is over. Peak power potential is higher, but the big turbo just can't recover from a decreasing exhaust flow volume, again even if very brief. Recovery is best achieved with a 30 series turbo matched with a 71 or 76 series compressor wheel... if this is something that matters to a racer.

to be fair sled prices and taxes in canada a freaking outrageous. I bet that build would have been 30k even here in the states and that is a bargain for a sled built by a shop like Precision or H&H

Thank you. Canadian taxes alone on that amount are $4,500+ and sled cost is typically $2,500 higher in Canada. It is all about nuances I guess.