Boondocker Apex: 360hp at dynotech

[hallnracing]

New to yamaha, and this is my first post, on this forum. I have never had much respect for the four strokes, as the power to weight ratio is just way inferior to a modern two stroke. This is easily fixed, however, with the addition of a turbo. A brief overview of my experience helping Jason Stoviak with his boondocker apex turbo kit. We started out with the basic kit, using the gt25 turbo and 9:1 JE pistons. Was a blast to drive, and once traction issues were addressed, a seriously fast lake racer, even at a pump gas safe 10lbs of boost. As the winter progressed, gradually turned up the boost and started running race fuel. Found the stock fuel system good to about 13lbs. Ran it at 14lbs some, but a/f ratios getting a little lean. The additon of boondocker's larger injectors allowed for safe a/f ratios at 14lbs (and much more power). Boondockers fuel controller allowed adjustments to maintain low speed drivability with large injectors. Attempts at 15lbs found the stock fuel pump inadequate. Next was upgrade to the gt28 turbo and high volume fuel pump. WOW! this thing is crazy at 17lbs of boost. Ran out of weight for the clutch to attempt running any higher boost, and the ice and snow were about gone by then. By now, we are pretty well addicted to boost, so it is off to the dyno. A trip to Dynotech research, in Batavia NY revealed the incredible numbers possible with this kit. Made numerous pulls at various boost settings, until we burned the last of our Klotz 118 fuel. Lowest boost was 14psi. I am not sure if wastegate tweaks could have gotten it lower, as we weren't interested in going that direction. At 14psi, 12.1:1 a/f ratio, made 259hp. We kept turning up the boost, a little at a time. 360hp at 27psi, 10.9:1 a/f was where we stopped. Every turn of the boost knob was producing more boost and hp, and it seemed we could go much more, but we thought this was enough for the stock rod engine. I am fairly experienced with two stroke trail and race engines, but this is my first turbo experience, and I just can't believe how relatively cheap and easy it is to get huge power. These numbers are with stock cam and ignition timing, and completely stock engine, other than low compression pistons. Boondocker fuel controller allowed adjustments as we changed configurations throughout the winter. Rocky and Dave, at Boondocker were great to work with, making my first four stroke experience a good one.

 

[BlueByYou2000]

Glen, Welcome to the site. Does this mean your done with your big Cats? If so, team blue just got one hell of an addition. Again, welcome and enjoy the site...BBY

 

[hallnracing]

Thanks for the welcome! No worry, I'm still a Cat guy. Just helping out on this project and I have learned a lot - still relatively ignorant in the ways of the Yamaha.

 

[dynotechjim]

I've just posted a tech article and some of the key Boondocker Apex turbo dyno sheets (13.5, 14.5, 17.7, 26, and 27.5 psi) on my website dynotechresearch.com.

 

[ken_climb]

Boondockers has come a long ways this year! Keep up the good work!

 

[dynotechjim]

The Boondocker GT28RS upgrade that we tested on DTR.COM requires larger injectors and an extra fuel pump, but for cruising those big injectors will drown the engine unless your fuel management system can reduce fuel flow like Boondockers are well suited to do. Even F7 Firecats benefit from reduced fuel flow, where Boondocker with their ability to shorten pulse width has the advantage. I've dynotuned maybe 100 EFI Firecats with Boondocker control, and the ability to reduce fuel flow in various ranges is key to their ultimate success here, and the customers' success in the field.
While we made 370 HP cold stab with the GT28RS, the Boondocker fuel system (pumps, injectors and Boondocker box) is surely capable oof delivering much more HP with an upsize turbo. I suspect that with the Boondocker/ large injector package 450+ HP is doable with a bigger, but slower spooling turbo that would be less fun to drive on the trail but would perhaps be fun on the mile long radar runs if you can add enough clutch weight to keep it under the rev limiter.
Boost is good stuff; just please match octane to boost level.

 

[jaleebi22]

I've been a member since day-one...well worth the price of admission...................!!!!!!!!!!!!!!!!!!!!!!!!!!!!


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