2008 ROUSH Stage 3 Build...Take III

[AutoXRacer]

Yeah, the new pistons are only a -11cc dish, that is not going to lower boost. It's upstream... Blower, rotors, throttle body...

 

[thump_rrr]

Yeah, the new pistons are only a -11cc dish, that is not going to lower boost. It's upstream... Blower, rotors, throttle body...

I've been following this build from the get go and now I'm puzzled.
Didn't you replace the crank pulley for an under drive unit?

Let's assume the blower, TB, pistons, and heads didn't change for a minute.

If you reduced your crank pulley from 7.4" to 6.55" you would need to change your blower pulley from a 3.0" to a 2.6" to keep the same drive ratio.

 

[DiMora]

What is your current crank and snout blower pulley diameter and what redline do you have set?

Trying to calculate whether you have room to spin the blower faster and pick up a PSI or two...

My guess is the TB costs you a bit but I'd keep it "because streetcar"

 

[thump_rrr]

A dual 68mm TB is the equivalent of a 96mm single.
I doubt that has any sizeable loss.

 

[AutoXRacer]

I've been following this build from the get go and now I'm puzzled.
Didn't you replace the crank pulley for an under drive unit?

Let's assume the blower, TB, pistons, and heads didn't change for a minute.

If you reduced your crank pulley from 7.4" to 6.55" you would need to change your blower pulley from a 3.0" to a 2.6" to keep the same drive ratio.

I did buy an undrive pulley; we all though this blower was going to make more boost. I installed thE 6.55 first with a 3.0 upper and we only got 7 psi.

Then I swapped the 3.0 for a 2.8 and got 9 psi.

Lito told me to remove the 6.55 and replace the 7.40.

So with the 2.8 and 7.40 we only got 12 psi with a creeping peak of 14 psi past 6200 rpm. From the graph above, you can see the blower starts making boost starting at 6250 rpm.

What bugs me is that this pulley combo (2.8/7.40) made 16 psi on the previous motor. Technically I'm down 4 psi and 2 psi at 6250 rpm.

 

[AutoXRacer]

What is your current crank and snout blower pulley diameter and what redline do you have set?

Trying to calculate whether you have room to spin the blower faster and pick up a PSI or two...

My guess is the TB costs you a bit but I'd keep it "because streetcar"

Current setup:
Upper 2.8"
Lower 7.40"
Max RPM 7500

My current TB is a dual 67mm.

 

[AutoXRacer]

A dual 68mm TB is the equivalent of a 96mm single.
I doubt that has any sizeable loss.

I also don't think I'll be seeing any improvements with the throttle body swap.

 

[BruceH]

If you are using that compression height with a 3.750" stroke it's still .030" more in the hole than compared to a normal stroker compression height of 1.200". If that's the case you will be down on compression and power. If you are using them with a 3.800" inch crank then they are likely sticking out of the hole.

Hopefully I've missed something else you posted because either scenario is not ideal.

Good thing I like to take pictures... LOL

So here is the MMR piston box:

-11cc

Now waiting to hear back from JDM to see what their pistons are...

 

[hamish]

So with the 2.8 and 7.40 we only got 12 psi with a creeping peak of 14 psi past 6200 rpm. From the graph above, you can see the blower starts making boost starting at 6250 rpm.

Not to be a technical dick here but you make "boost" instantaneously with that graph.

What cams are you using?
Did you time this motor yourself?

 

[AutoXRacer]

Not to be a technical dick here but you make "boost" instantaneously with that graph.

What cams are you using?
Did you time this motor yourself?

123450 timed at 4 degrees retards for a centerline of 109.
Yes, same cam timing as before.

Bruce, I have the 3.80 stroker crank; the piston tops or ring land was flush to the deck of the block. Piston did not protrude nor was recessed into the cylinder at TBC.

Not like you can tell anything from these pics. lol

 

[BruceH]

123450 timed at 4 degrees retards for a centerline of 109.
Yes, same cam timing as before.

Bruce, I have the 3.80 stroker crank.

If you are using 5.850 rods then your pistons are sticking out of the hole and into the head gasket about .012". That would push compression up quite a bit. I think you would of noticed any ptv contact. Did the assembler mention that the pistons were out of the hole? Did they take ptv measurements?

Maybe the info on the box is wrong. Is there any chance mmr used a used box to send the pistons in?

 

[AutoXRacer]

If you are using 5.850 rods then your pistons are sticking out of the hole and into the head gasket about .012". That would push compression up quite a bit. I think you would of noticed any ptv contact. Did the assembler mention that the pistons were out of the hole? Did they take ptv measurements?

Maybe the info on the box is wrong. Is there any chance mmr used a used box to send the pistons in?

No he did not mention it...

All I know is when I set the TDC without the heads on, the pistons did not protrude from the block/cylinder. They were flush with the deck.

Frankly, I don't trust MMR. The info they give you is very inconsistent.
I wish I would have had my builder cc the pistons. But again in my innocence, I trusted MMR supply me with the correct parts. Not saying the parts are wrong, just wish they provided better consistent data.

 

[AutoXRacer]

Lito requested I take pictures of the plugs... Here goes boss!!

Cylinder 1

Cylinder 2

Cylinder 3

Cylinder 4

Cylinder 5

Cylinder 6

Cylinder 7

Does 7 seem a little wet...?

Cylinder 8

I did have additives in the tank...a whole can of Sea Foam and 1/4 can of Torco...

 

[AutoXRacer]

Regarding the piston tops... I think the coating is gone!!
What do you think?

Cylinder 1

Cylinder 2

Cylinder 3

Cylinder 4

Cylinder 5

Cylinder 6

Cylinder 7

Cylinder 8

You still see a hue of red...but its not like when new...

 

[BruceH]

I hate to ask this but I have to. Did you check with a depth gauge or your eyeball? How about a fingernail check for protrusion?

No he did not mention it...

All I know is when I set the TDC without the heads on, the pistons did not protrude from the block/cylinder. They were flush with the deck.

Frankly, I don't trust MMR. The info they give you is very inconsistent.
I wish I would have had my builder cc the pistons. But again in my innocence, I trusted MMR supply me with the correct parts. Not saying the parts are wrong, just wish they provided better consistent data.

 

[AutoXRacer]

I hate to ask this but I have to. Did you check with a depth gauge or your eyeball? How about a fingernail check for protrusion?

No, I did not go into that detail. Just eye ball.

 

[Wes06]

Bahaha. If the coating is gone I will laugh because MMR sucks.


Sorry bout the problems your having though

 

[AutoXRacer]

No problems really, motor runs great.
But I would like to know why I'm down 4 psi.

 

[thump_rrr]

Bahaha. If the coating is gone I will laugh because MMR sucks.


Sorry bout the problems your having though

You have no heart If you would laugh at a man who is on his 3rd engine build.
Karma is a bitch.

 

[thump_rrr]

If you are using that compression height with a 3.750" stroke it's still .030" more in the hole than compared to a normal stroker compression height of 1.200". If that's the case you will be down on compression and power. If you are using them with a 3.800" inch crank then they are likely sticking out of the hole.

Hopefully I've missed something else you posted because either scenario is not ideal.

can you please explain how you get your calculations?