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After spending a day dyno testing Monday what we had on the F7, now it appears as though results may be skewed due to our pulling the hood off the sled, and leaving it off while we installed aftermarket reeds and airbox mods. The sled owner, Kim Stout from Williamsport PA found out from his dealer today that if the headlight assy is not working (like if the hood is removed during dyno testing) the ECU goes into some sort of limp home mode. We did all baseline testing with the hood on, headlight operating. To install the aftermarket reeds, the hood was removed and left off for all but the last two or three dyno runs where the F7 mysteriously leaned out some (fuel flow lb/hr dropped) and picked up 4-5 HP over baseline.
Our baseline, hood on, bone stock was about 130hp at 7500 after 15 seconds of WOT run time. BSFC was .80+, safe for 85 octane forever. No difference if the air was sucked through the waterproof membrane or through a wide-open airbox inlet. Attaching the SuperFlow airflow meter to the stock airbox opening, we peaked at 248cfm. Then we pulled the hood off, installed the reeds, airflow was again peaking at 248cfm with identical peak HP, but midrange airflow and HP was higher with the reeds. But did the removal of the hood/ headlight reduce ignition timing as Kim's dealer suggested? I should note that measuring the pressure inside the stock airbox gave us 5" of water pressure negative at peak airflow (5" water pressure = 1/5 psi negative = the amount of suction force necessary to suck CocaCola 5" up a straw = not very much). Adding 5 D&D bullsey filters reduced that peak negative pressure to 1" water pressure. Every bit helps.
Note- our 7500 rpm power peak is with what we call trail-typical pipe temperature. The dyno tells us that after 85 seconds at WOT, the power peak slides up to 8000 rpm because the exhaust gas inside the center section is increased due to the heat soak of the steel tuned pipe (hotter gas = higher speed of sound = higher RPM where peak HP occurs). This is dead accurate digital RPM, much more reliable than stock tachs which must be calibrated.
The exhaust valves open at about 7200, fine for the 85second at WOT pipe, but way late for a normal trail operated pipe. How can we open those valves earlier?
Can anyone attest to the ECU limp-home mode if the headlight is not functioning?
More to come as we figure this out. Another test session is planned.
 
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Discussion Starter #2
one other item of importance-
Kim's sled had a ECU with a square code. We tested another F7 owner's box with a triangle code, and we got identical dyno results, same fuel flow lb/hr and same HP, but again this was with the hood off/ no headlight. Maybe we have to do that again as well with the hood on.
 
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Discussion Starter #8
yes there is 137+hp available, but not with .80+ BSFC. This engine (like our stocker tested for AmSnow shootout) stock made 130, but if fueled like we like them for our style of riding will make much higher power with only fuel adjustment that approximates the numbers youre talking about.
130 HP x .80 bsfc = 105 lb/hr fuel flow (that's what the f7 ECU delivers at 700 ft altitude, 30 degreeF). Lean that down to 95 lb/hr fuel flow and you easily get 135 HP x .70 BSFC = 95 lb/hr fuel flow which is what we think is safe for long multi-minute wot runs on 92+ octane gas.
 

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Jim, I have ordered the Thunder Products intakes and the Speedwerx Intake tube for the sled. Should be in shortly. I have a line on a set of V-Force reeds that I can borrow. Let me know if you need another test sled. I just have to check my pistons first. The check engine light was coming on. Just want to make sure its still all there. Email me or call my shop if you want to try mine also. 716 754-7646. Bill
 
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Bill- I will try to call you tomorrow, we need to follow up on all of this to see what is going on.
 

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Jim, did you have a chance to compare the stock digital and/or analog tach to your dyno's tach? Gosh, peak [email protected] RPM sounds very low to me, as I've been very happy with my F7 so far running her with box stock clutching between 7900-8100 RPM... on the sled's stock digitach. This info has me a bit comfused. Also, with all the talk of the F7 being a 140 hp sled, 130 is a bit disappointing to say the least.

Just a few things to check before your next (when is it?) F7 dyno session:

* Make sure the APV valves are clean and operating correctly

* Make sure the clear vent tube coming out of the ECU box (on the airbox) is
not plugged by water, snow, ice, or grease

* Make sure compression is good and within spec for this motor

Thanks for sharing your info and results with us here on this web site. Looking forward to the next F7 session report! -- Roy
 
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I sent my temp gun to Bill for him to use this weekend to see what range pipe surface temp he's running, as well as cyl head surface temp so we can try to duplicate those conditions. He's got some stuff on order, if it comes in Mon we plan to dyno test Tues or Thurs. It should be fun to try one of those special ECUs while we're at it. No we didn't check tach, but we should try Bill's. Everyone needs one of those $85 digital Stihl chainsaw tachs to calibrate their sled tachs with.
 

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DynotechJim, I'm wondering if the "Forced air induction" of the F-cat will skew dyno numbers down. I don't know a damn thing about dynoing and maybe this question has been beat to death. Just wondering....Mac1
 

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Originally posted by DynoTechJim@Feb 22 2003, 08:16 AM
No we didn't check tach, but we should try Bill's. Everyone needs one of those $85 digital Stihl chainsaw tachs to calibrate their sled tachs with.
LOL... I've already got my old $250 Digitron tach AND a $250 tach calibrator, but I haven't put much thought as to how to hook up the Digitron, or how to check the tach on this new gauge, especially the digital part. Anyone know how to do this on the new gauge without blowin' it up? I've been assuming that the stock digitach and speedo are accurate, but I should know better than to assume anything I suppose. On your next F7 session please check Bill's stock tach (digital AND analog?!) against your dyno tach. Thanks Jim! -- Roy
 

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Stock tach is right on in digital mode or using max recall. Not sure on analog mode. Speedo seems pretty accurate as well. Verified on Dynojet track dyno.
 
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Discussion Starter #16
What about a timeing key,do they give you 2 hp at the track???
 
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mac1- looking at the hood air intake I can't imagine that there can be any "ram air" effect inside the airbox. To be sure, it could be verified by measuring airbox pressure at 100 mph. Maybe I can get Bill to test that after our dyno session next week. Note that stock on the dyno with no high speed airflow was -5" wp which is not much.
RoyT and BigGun- tach testing is so critical, if you use our dyno results to help tune your own machines. However you do it, the tach calibration is something that has to be done. I recall that early piped Polaris triple tachs often varied 500-1500 RPM at peak which made them almost worthless for clutch tuning to our data. Those neat Stihl chainsaw digital tachs clip on to the sparkplug wires, and give RPM data exactly identical to ours. That is a great tuning tool for $85 or whatever they are today.
tunedF7- the timing key should be fine for peak HP, but midrange HP/ fuel flow is close enough to max that extra timing could be detremental if you operated your sled in heavy snow that pulled revs down below peak power RPM; A/F ratio and BSFC is lean and crisp below peak HP (where it is fat and ultra safe) and there not much leeway there in the important midrange to cheat mother nature.
 

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DynoTechJim so your saying that it would be ok to use the timing key in 660' drags at wot...but not for trail,i also have reeds and air intake,and should i use 92 octain or the 87...Thanks
 

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JIM, IF YOU WANT TO MAKE IT LEANER, TURN THE THROTTLE POSITION SENSOR FORWARD(CLOCKWISE) 1/16TH OF AN INCH AT A TIME. MAKE A PEEN MARK ON THE TPS AND THE THROTTLE BODY IN THE STOCK POSITION BEFOR ADJUSTING SO YOU CAN RETURN IT TO STOCK WHEN YOU ARE FINISHED. GOOD LUCK.
 
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