#64 Upgrade Update

[Scott McKay]

I put the entire trick flow package on the #64 last week. End result, 317 HP 297 TQ. Of note, the fuel injectors are critically undersized at 24 pounds, so run the fuel pressure up to 60psi (not a joke) and start from there. Don't run the car hard without having it on a dyno with the air/fuel being monitored or its likely you will run it lean and blow it up. Mine liked 14 degrees of initial timing best and my final fuel pressure was 60psi.

At Sebring, which is a long, flat power track, the car was roughly 4 seconds a lap faster than the old stock challenge racer, and I was doing it with old beat up tires. The new challenge racer will roll by American Iron cars like they aren't there.

-Scott

[riptide motorsport]

4 seconds?..........thats huge!!!!!!1

[rschoeni]

Long course? What kind of lap times did you turn?

[Jim Schenck]

Scott,

The 24 lb injector rating is at 39.2 PSI, at 52 PSI they are flowing a 27.7lb/hr, which is enough to support our ~380 flywheel HP at a conservative 85% duty cycle. I think if you get your car back to the dyno with a working wide band you will find it is a little bit rich at 60psi and that is also why your torque is a little low compared to some of the other cars. I think where most guys will end up is running between 50-55 psi and 16 deg of timing, but I completely agree that it is better to start safe with high pressure than the other way around.

Bob,
Both John and Scott were running around 2:25 flat, I think john has his qualifying lap on video now.

[rschoeni]

Mechanical upgrades aside...That's some driving talent right there. :)



Bob,
Both John and Scott were running around 2:25 flat, I think john has his qualifying lap on video now.

[ED@TFS]

I love hearing These kind of numbers, if you have any video lets see it. :-)

[johngeorge]

videos
Scott McKay's Saturday race: http://vimeo.com/39831420
JG Sun Practice fun in traffic: http://vimeo.com/39833615
JG Sun Quali fastlap: http://vimeo.com/39705979
JG Sun Race 1: http://vimeo.com/39729025
JG Sun Race 2: http://vimeo.com/39731725

[vnmsss]

Thanks for the update Scott. 4 seconds/lap is impressive, and I'm very encouraged with the initial performance of the new Challenge Series configuations.

In regards to the tuning, Tom Coon had the same experience as you, in that the car ran dangerously lean on initial tune.

Jim or Eddie.....I appreciate your expertise in this area.....I've been concerned that the 24# injectors might be a bit undersized, especially considering the air flow of the new Trick Flow heads (which is awesome!)..I am thinking a 30-34# (@43 psi) would have them "under" working themselves, as opposed to 24# operating at the upper limit of the flow/duty cycle.

Is there a reason not to go with a bigger injector and run a lower pressure and maybe less timing? Spray pattern at 60+psi would not be optimum either, so amping that down would be reason alone....Possible heat soaking of the injectors from running at close to a 90% duty cycle for a 30-40 minute race might become issues as well....My understanding is that an injector can only cool when it is closed...The ability to diagnose and tune the new configuration by placing the car in the hands of a competent dyno tech with the ability to read/adjust the runing parameters seems of paramount importance as well....Again, I appreciate your expertise, and the opportunity to learn the nuances of tuning the new system.

Thanks again Scott, and good luck this season (not that you need it!!!)

Karen



I put the entire trick flow package on the #64 last week. End result, 317 HP 297 TQ. Of note, the fuel injectors are critically undersized at 24 pounds, so run the fuel pressure up to 60psi (not a joke) and start from there. Don't run the car hard without having it on a dyno with the air/fuel being monitored or its likely you will run it lean and blow it up. Mine liked 14 degrees of initial timing best and my final fuel pressure was 60psi.

At Sebring, which is a long, flat power track, the car was roughly 4 seconds a lap faster than the old stock challenge racer, and I was doing it with old beat up tires. The new challenge racer will roll by American Iron cars like they aren't there.

-Scott

[FFSpecRacer]

My fuel pressure is set at 43 pounds and timing is 15 degree.

A/F is 12.5 from 4500 up and actually gets a little fatter at the top end.

[Jim Schenck]

The 24 lb injectors aren't a concern with our capped horsepower levels, if we were going to be pushing 350 at the wheels down the road then going to 30s would be better. Also these are the same injectors we have run in the 85 car for the 25 hour with the same power level, so no problem running 40 minutes.

[vnmsss]

Thanks Jim!

[FFRSpec72]

videos
Scott McKay's Saturday race: http://vimeo.com/39831420


Scott needs a new camera !