Tuning my DR750s on Chrome

[futurevr4man]

Be safe, Christopher! Your wife may kill you if you blow it up again!

[Chris@Rvengeperformance]

Be safe, Christopher! Your wife may kill you if you blow it up again!

I don't know if she'd kill me, but the car would sit for a while!

[Chris@Rvengeperformance]

Now for which?

all of them!. Two sets in parallel.

[familyMAN]

Changed my mind; go 16g. Loved my billet td05's with the 74. 16g's will spool like the 750's did on the 3.0.

[futurevr4man]

I know you have made up your mind, but I think you should really go the 16g route. If I had you on recorder from last time we hung out, I'll bet you could convince yourself even. I am just scared for your bottom end... even if you take out the timing, 20psi at 3000rpms is just straight hard on the bearings. I'll bet jfast could write a few pages of equations showing the pressure on the bearings varying by rpm. Slower rotational speed means more force in a generalized area for longer (which is why you make torque at lower rpm as well, obviously). I'm just thinking out loud really

[Chris@Rvengeperformance]

Definitely still considering all options. I may toss the 750s up for sale and see if there are any takers since the 16G kit isn't getting bites yet.

[Chris@Rvengeperformance]

Changed my mind; go 16g. Loved my billet td05's with the 74. 16g's will spool like the 750's did on the 3.0.

you really think it will spool that fast? I figured I'd still lose 500 RPM. It is hard to make a direct comparison with the data I have seen. I'm not sure I have seen one 3.5 16G car running e85 and was ironed out.

[familyMAN]

you really think it will spool that fast? I figured I'd still lose 500 RPM. It is hard to make a direct comparison with the data I have seen. I'm not sure I have seen one 3.5 16G car running e85 and was ironed out.

You are adding about 16% displacement. (I'm not sure what the exact displacement is on stroker.) Take a typical 16g spool number at x psi at y rpm and drop the rpm by 16%. It worked out to EXACTLY that on my car when comparing the 3.5 NA heads/cams to my 3.0 with the same NA Heads/cams.

Of course different setups affect spool and tq but it will give you a general idea. I'm sure ray could give you the real world examples since he has probably tuned quite a few 16g cars, including the 16g stroker.

[HLxDrummer]

Haven't been following the entire thread but if your worried about power down low, can't you:
A) Don't go WOT until higher RPM (I do this with 9Bs or I'll get knock at low RPM/high load). If you want to go fast, downshift. I'm sure you can pull a hill as you would in a normal car in a normal gear without killing the engine
B) Pull timing
C) Adjust your boost controller to give you less boost at low RPM

Either way, good luck! It must be hard having to put all this work into your new car/build!

[kywhitelightning]

Slower rotational speed means more force in a generalized area for longer (which is why you make torque at lower rpm as well, obviously). I'm just thinking out loud really

TQ is made more down low because of more time for cylinder filling of air. More air more means more fuel required and more TQ will be made. DR750's spool fast which helps pump more air into the cylinders in low RPM's than all the other comparable turbos. Camshaft profile has a major part to play in that as well but I doubt anyone in there right mind would purchase a camshaft profile that adds TQ down low and in turn sacrifice top end HP especially in an aready small displacement engine.

The only other ways to increase TQ is to increase displacement via crank throw(stroker) or overbore.

Jeff