lost rpm

[max rolph]

SO swinging this to TY forum, have 2020 t-cat 998 with stage 4 TD... have everything from eco tune to MAX 20, header, super quiet 3", smart blow off, big intercooler, programmed wastegate, Charge tubes, TAPP primary and STM sec 46/36 helix green snow pro and GAP closed loop and GAP flaher. Storm track and 144 trigger up centre. sled when first done would pull 9000 rpm and now fighting to get 8800, will run 85-8600, i used to have med bolt and 4 washers per bolt now im empty with short bolt. nothing has changed and my rpm i cant get back... was at TURBO DYNAMICs ysterday, 5 hours drive, we did wastegate upgrade and am getting 20-22lbs of boost on MAX 20, but will not rpm, changed clutch to stock primary and was able to see 8900 but then dropped back again... on log boost is consitant and tps is 100% AFR is at 11.9-12.0, no knock or ping count .
my thoughts were weakened spring in TAPP, but still with stock primary not getting rpm.... any thoughts? anyone else exp this.
ENGINE runs perfect, temp good, no antifreeze leaks, always run 97 octane, put brand new elbows on throttle body and new clamps. everything looks tight no leaks.... and boost gage shows 20lbs instantly and stays.

 

[STAIN]

put brand new elbows on throttle body and new clamps

Did you trim the barrels on the intake clamps? Also try to throw the stock secondary on to see what happens. STM helix angles on Yamaha helixs are known to be about 8 degrees higher, not sure about the CAT style helix.

 

[stevewithOCD]

If Mr KNAPP chimes in, he's gonna yell at you until you do what STAIN said.
Cut the spacers on the Throttle Bodies in half.

LISTEN to HIM!

Many found that it's only the high boost where you see this problem.
They don't seem to leak on lower boost at this area.

 

[Crossfire12]

It’s the intake temps, hot!!

 

[max rolph]

Soo hers latest... PS thanks for all the reply's by the way... its like a family on here!!! cuz we cant do anything else right now!!

Unloaded sled after coming back from TD, by the way they were baffled as well... still are actually, i just had the upgraded waste gate done as they did a filming of the installation for web. we thought this would fix problem. not. $1000,00 later but i was getting that done anyway.

Anyway ... started sled... runs PERFECT,,, idles right at 1650-1700rpm, stuffed a ragg in muffler and it stalls within a second or two proving their is no header leak or exhaust leak did this several times at a little throttle just to see if i could hear any exhaust leak... nothing!

Took hood off and disconnected charge tube from turbo and put a pvc blocker in end, then hooked air line up from my compressor and pressurized the whole system and then turned engine over by hand untill the valves were all closed and the system held presure at about 30-40 psi... maybe more as i had no gauge...my whole garage is plumbed with air lines from 60 gallon ingersol rand air tank thats at 100psi. soo i pumped air in till you could not squeeze the charge tubes.... discovered one squeal leak at a clamp on the intercooler... but only sqeeled like a mouse at @40psi, so tightened that clamp and stoped the squeel, held the pressure and sprayed soap all over the entire system at every joint and clamp... hell even my turbo smart valve was GOOD... no bubbles anywhere!!!

Took TAPP appart and checked everthing and spring is supposed to be 190lbs compressed and thats what it measures at... soo thats ok, the clutch looks and feels brand new... there is only 600k on it anyway. put it all back together and put it back on.

im using XS827 belt, will try the XS829 or the factory and see.... but just does not make sense since i had rpm before with same combo... but that was when belts were new as stated, ill try these others and see what happens.

only other thought was if timing chain was jumped but then it would run crappy at idle and there has never been any abuse to this sled. i use only 0w40 full synthetic oil and K&N oil filter and oil level is always perfect and same goes for antifreeze, this sled has never been over 180deg even going dwn a road... always runs at 172 deg on trail... have never had to put scratchers dwn yet.

testing at TD was at -10deg and intake temps were cool.

 

[stevewithOCD]

Mine has the exact same problem.
I can't test for boost leaks until i get home next week.
I took off the TAPP & Pro4 to put on what worked last year even though i know it's motor.
I'll change plugs if i find no leaks.

 

[max rolph]

you knows its going to be something obvious... soo to discount the belt, i changed to the stock cat belt 114 and will try even thou the xs827 still looked like new but has been on for 600 miles. but weirder things have happened. i have also never changed plugs... but it doesnt miss a beat... runs smooth as glass

 

[stevewithOCD]

WELCOME MAX!

I probably should have started with that

 

[stevewithOCD]

My riding area is 6 hours away and with NO snow, testing was impossible since this only happens on the top end.
Need a lake or rail road bed to really see what's going on & a Data Logger would really help.
OH well, i'm going riding and it still pulls like hell!

 

[STAIN]

Steve, Have you ridden it since trimming the clamp barrels?

 

[STAIN]

I also wondered if the plugs need to be re-gapped. Higher boost will blow out the spark and the plugs will need a smaller gap. When this happens though it feels more like a skip.......

 

[vmxrdr]

Our map sensor fails gave exactly these symptoms. Have 4 bars and new tunes on the way.

 

[max rolph]

Our map sensor fails gave exactly these symptoms. Have 4 bars and new tunes on the way.

Extreme... i have 3 bar sensor, did it run fine but just lost rpm on top? thats all mine is doing.... wont pull rpm no matter what we do, light weight in clutch... wind up secondary... change clutch... over 20lb boost and no knock or ping count.... no leaks anywhere!!! clutchs have no slip marks.... pulls hard even at 8600 but wont go to 9000

 

[vmxrdr]

That is exact symptoms we had, diagnosis is really easy if you have access to a different sensor to swap in. We had an earlier production one that fixed it instantly.

 

[max rolph]

but with a bad map sensor would it not run like crap all the time?? mine starts ... runs great... just no RPM increase or very little increase going from 285 tune to a 330 tune/17psi to 20psi... runs good at all spots just wont pull rpm.