A Little Top End Tuning Help Please

[kidturbo]

Hit a snag with testings last weekend. The shifter linkage in the outdrive snapped a bolt and got stuck in FWD. So took it easy until I made it back home Sunday. Attempting to fix that issue today.

Did see it hit 3750 on the digital tach in a race against a twin 454 engine boat last Friday. Had the smaller prop on there and just stayed in it at WOT for about 10 seconds watching the EGT gauge laying on 1650... She was trimmed up nice and walking away from a 80+ mph boat. I said you'll GO or BLOW bitch..

She took it and liked it..:rofl: Carved two notches in the shifter for that win.

 

[kidturbo]

Turbo Swap

What's the consensus on replacing my 1.06 A/R 4094R with a 1.28 4294? It has a similar compressor map to the 40 with the same T4 base, but better CFM air flow on the exhaust side. Uses 4" exit vs the 3" I have now.

Would be giving up the water cooling and ball bearings, but maybe some EGT's also. A little smaller than the 1000hp 4202, which I'm not sure I could spool up with my current build.

-K

 

[JoshH]

What about a 4294R? Then you don't give up the water cooling and ball bearing. Or better yet, a 4202R.

edit: or, how about a GTX4202R?

 

[kidturbo]

The GTX is a nice unit, but not commonly found used. 3k isn't in the budget this month for a new one. GT4294's are out there, and fairly cheap. Figure I could about break even on my used 4094R.

That 4202 looks pretty big compared to what I have now. Any experience with them? Since I'm limited by what the drive can handle, no need to go over a true 800hp unit.

Right now I start to spool around 1200 R's, which is very good for getting the boat up out of the water quickly . Also need to say with a 4" outlet max if possible to work with the existing water cooled exhaust pipes.

-K

 

[CurtisEmery]

A 4294 or 4202 will make a ton more power than the 40 series turbine wheel. I say go 4202 and be done with it. the 1.28 should make lots of power in the higher rpms.

 

[TeaBagger2006]

X3 on the 4202r with the 1.28 housing

 

[kidturbo]

Thanks guys. I'll keep searching for a good 42xx.

While waiting on a new T4 gasket to arrive in the mail to get a true drive pressure reading, I remapped my MAF B0201 table with the LBZ numbers. Made a good difference down low, she rolls coal again when spooling. Comparing past years logs, it looks to been reading low, just cleaned the MAF so I wondered why.

Learned a couple things, first the MAF comes into play no matter what the DSP tables say. Second, seemingly little modifications to the air intake can greatly impact MAF readings. I realize mine is not in a ideal location, but was reading within factory specs until I added a velocity stack with a screen above the 4" elbow pipe. Noticed the readings fell off by 2lbs per minute at idle, and were off by 10-15 up high. So I decided to try these newer calibrations. Didn't help building higher rev's, but it now looks much better against the turbo map...

Has anyone ever bench calibrated a MAF tube? I understand it's not vital to big end power, but might help in understanding the true turbo performance. Contacted a friend with a flow bench today, am gonna try and chart the voltages on that up to his 600CFM limits

-K

 

[CurtisEmery]

Drop the PW to 1800 and raise rail PSI desired to 175-180 MPA, see if lower PW and more pressure helps.

Also I hope you shut pilot injection off above 2600 rpms......

I would also listen to what this man has to say. He is very good at finding tuning issues and solving them:thumb:

 

[kidturbo]

Actually was clearing room for that new config earlier tonight.

My primary running "DSP1 position" tune is fairly close to his setup. 1750us @ 160mpa and 26*. It's a very stable tune with good power up to about 3300R's and lower EGT's than the 2000us I've been running. The 2000us just pulled harder up top, so I've been stuck on playing with it..

I'm also not sure it can currently maintain 180mpa fuel pressure. Have a pump to rail line fitting that starts leaking above 22000psi.. Find a puddle in the valley that only shows after hard WOT runs. Have attempted to resolve it twice now, gotta replace the line and CP3 outlet fitting I guess.

I do understand where he is pointing me. Now that the MAF readings seem back on track, I feel better about adjusting fuel tables again. Just hard to justify adding more fuel when the air flow amount was landing in the left side of the compressor map. My T4 gasket arrived today also, tomorrows project list.

BTW, pilot is set to 0.00 at 65mm3 & 2800 and beyond. :thumb:

-K

Log From Last Sunday.

 

[CurtisEmery]

Sounds like you are heading down the right track! Get that larger turbo on there already lol! Sounds to me like you are out of air flow and past your hp peak. That gt42 turbine should raise your peak power rpm a bunch. Good luck:thumb: