Originally posted by EricL
Is there a way to just ask Comptech, "Hey, how would the S/C work on my car if added an MDX bottom end (later)?" "Would I need to consider any changes or issues?"

The other steps you have mentioned seem reasonable places to go from here. (open IMRC, lower boost).

Wish I had magic bullet, but...

Originally posted by sgmotoring
How did you come out with 11.26 to 1 compression ratio? What kind of assumption did you have to make in your calculation?. I thought my engine have no more than 10.2 to 1 compression ratio.

Part of the comments refer to questions asked about Syncivic’s 3.5L mods, and other issues (compression) just refer to compression ratio issues.

I posted this earlier, and here is the "paste from the earlier post". BTW, I didn't count on the fate of the planet depending on every detail and assumption being "dead-on", but here it is:

"1. I believe the crank gets some chamfering to make for "better lubing" (as to SERIOUS work -- I don't think so).

2. The compression ratio is based on:

CV (cylinder volume) # the volume that is SWEPT by the top of the piston
CCV (combustion chamber volume) # the area above the piston at TDC (AKA unswept volume)

CR (compression ratio) = (CV + CCV) / CCV

3. The "slugs"/"pistons" are changed from the MDX to different pistons that allow for less compression (than with the MDX slugs) (Note: I can’t know for sure, since I haven’t seen the pistons, but I’ve included some math that will predict combustion chamber volume and compression ratio and the change in them (based on the pistons and wrist pins being identical). I’m making a guess, but based on the increase in compression with a 7mm increase in stroke, the compression would increase from 10:5 to 11.26.

4. IF the MDX pistons (at top dead center) LEFT the combustion chamber volume (as it was with a stock CL Type S), the compression would be increased due to the increase in stroke. The "swept" area is increased with the shorter rod (in the MDX) and longer stroke of the crank. If both sets of pistons were flat top pistons or the Type-S pistons were reused (if that was even possible) the change in compression ratio would be from 10:5 : 1 to 11.26 : 1.

Ok, first some specs:

< --------------------------- >
CL Type S
CL
Bore and Stroke: 3.50 in. x 3.39 in. (89 mm x 86 mm)

Type S compression ratio: 10.5: 1
CL compression ratio: 9.8: 1

Total displacement (just for checking purposes): 3210 CC 3.21 liters

< ------------------------- >
MDX
Bore and Stoke: 89 mm x 93 mm (That is a stroke that is 93-86 = 7mm longer in the 3.5L engine (MDX factory short block)
Total displacement (just for checking purposes): 3471 CC 3.471 liters
MDX compression ratio: 10:0: 1


Derived figures (see math below for equations to get the values):

MDX combustion chamber volume (CCV) = 64.22 CC (based on 10:1 compression ratio.



So, how about some math?


First, figure the “swept” volume (not including the combustion chamber volume:

(We just need the area of the bore x the length that the area is swept)

Pi r^2 = Area = Pi * (8.9cm/2)^2 = 62.21 cm

Volume = Area * stroke = 62.21cm^2 * 8.6cm = 535 cc (cm^3)

Now just to check, we take the 3210 CC that Acura gives for total displacement and divide by 6: 3210 / 6 = 535 cm^3 = 535 cc for each of the 6 cylinders in the V6.

Time for the combustion chamber volume (CCV): [ CV = chamber volume, and CR = compression ratio ]

CR = (CV + CCV) / CCV and CCV = CV/(CR – 1) [CR = 10.5, CV = 535cc (for stock 3.2L CS)]

CV = 535cc / 9.5 = 56.32cc (So, the combustion chamber volume is now found for a stock CLS

Now, let’s assume that the combustion chamber’s volume stayed the same with the MDX slugs (the volume removed or added at the top of the piston would have to subtract or add the same volume as the original CLS slugs did). (A flat top piston for both would make this a no-brainer).

The volume is now going to be greater with the stroke increased from 86mm to 93mm (+7mm).

Volume = 62.21 cm^2 * 9.3 cm = 578 cc. (This is the swept volume in an MDX or 3.5 type s)

Just to check 578cc * 6 = 3.468 liters (and is close enough to the 3.471 liter spec given in the Acura MDX website blurb)


Ok, I’ll assume that a miracle occurs and the MDX piston is designed to keep the combustion chamber volume exactly the same; this would allow for an increase in CR.

CR = (CV + CCV) / CCV = (578 + 56.32)/56.32 = 11.26 : 1 (With MDX pistons with same volume removed or subtracted from combustion chamber or if assuming both pistons are flat topped (they aren’t).

AND, let’s check the math so far with the values I’ve obtained for a 3.2L CLS (no mods)

CR = (535 + 56.32)/56.32 = 10.5 : 1

If both sets of pistons were “perfectly” flat (flat top pistons), this would be done and one could assume that the stock block would give an increase in compression ratio from 10.5 : 1 to 11.26 : 1. (That’s assuming a bit, but it would be easy to see that it would be possible to have a compression ratio that is a bit to high for 91-octane and would probably move the requirement up to 93-octane. There’s probably a 2-percent gain there (5HP or so as well).

The pistons in $2500 conversion kit claims to have a compression of 10.85 :1. The combustion chamber volume would need to be reduced from a 3.2L engine (metal would need to be removed from the “slugs” when compared to the OEM 3.2L Type-S pistons (sitting at TDC). The change in volume to get the 10.85 would be CCV = CV / (CR-1). Solving for CCV we get: 578 / 10.85 – 1 = 58.68. The “new” pistons would have to “account” for a 58.68 – 56.32 = 2.36 cc increase in chamber volume (if the Type-s were flat top pistons, the pistons would have some small cut outs in the top.





Finally, if anyone wants to see if you can get some 0.050 oversize pistons, you can bore out the 3.2L to 3.3L and the 3.5L to 3.6+L …

As a note – with the shorter rod and longer crank, you are getting the piston speed to increase by around >10% and this causes the increase in lower and midrange torque/HP. The piston moves faster and gets the air moving quicker. The downside is the air speed at higher RPMS requires the heads to flow even more air – that’s one of the trade-offs…

The mean piston speed is also going to be greater at a given RPM. (This means there is more relative wear) Note: given the tranny situation, I wouldn’t worry about this AT ALL.)

Finally, a shorter rod doesn’t always mean more strength – it depends…

Originally posted by EricL
A possiblity...

There is just something very strange about that 6k bump and TQ rolloff.

Originally posted by sgmotoring
I think I found the problem. It is a loose supercharge belt, damn those belt need to be tight. I tighten it so tight that now my S/C belt tensioner is making a squeaky noise

Originally posted by sgmotoring
My fuel pressure was to low, 27psi with vacuum connected and 59psi with it disconnected. I couldn't adjust the fuel pressure to specs so I borrow a FPR from my friend NSX. Plug it in and my fuel pressure raise to 46psi and 66psi.

Originally posted by scalbert
But what is the pressure at WOT?? That base pressure without vacuum looks better but now the span is too low. You would like about 35 PSI with 20 inHg vacuum and 65 without vacuum.

I had a problem with my FPR which was swapped out and the car ran much better from then on as evidenced by my recent dyno.

Originally posted by sgmotoring
I think it is at about 75-80psi at WOT.

I am currently on a wired warranty exchange program with Comptech. I have to pay for the FPR and tensioner pulley in advance. They will then issue a credit when they recieve my old FPR and tensioner. I guess Comptech feel that there are just to many crooks out there.

Originally posted by Nashua_Night_Hawk
Scalbert is running close to 320 WHP!

Originally posted by Nashua_Night_Hawk
sgmotoring,

One word for you... YOUR RIDE Engine is messed up!... It needs major tune-up!... Go get your CLS to the hands of Comptech Tech to get it tuned!.

Scalbert is running close to 320 WHP!

Nashua

Originally posted by scalbert
That is too low at WOT; it should be up above 100 PSI at 5 PSI boost.

Comptech's policy isn't unusual, they are just covering themselves for when someone doesn't send back the parts.

Originally posted by darrinb
i'd get some toyo t1-s for ya on some light weight wheels..


get a hold of some 100 octane in cali and run the hbp,

u still have a lot left, tune it w/ the e-man and the new intercooler youd be on the back bumper of a c6 down the 1320

Originally posted by Ant7701
U can just contact scalbert for the tuning of the e-manage. His is allready done I believe and he can just tell u how to map the thing. I swear he's sponered by Greddy sometimes, he knows more about that e-manage than anyone. Scalberts like the father in My Big Fat Greek Wedding w/ the windex. You could be like...uhh my car rattles over bumps...e-manage. I'm gettin bad gas mileage....e-manage. My dome light doesn't work...e-manage. He's cool though and spent a whole shit load of time on it and helped out Modaddict like crazy so he should help u out a ton. Ohh and damn dude...I didn't even know u had the 03 headlights too. Shit it's like u live in my head man. I wanted to be the first PDG w/ the 03 headlights. Do u have the tails too, cause if not I got ya beat there

Originally posted by sgmotoring
maybe I can buy it from him, pay him to program it before shipping it to me? I wonder if that will work?

Originally posted by Ant7701
I swear he's sponered by Greddy sometimes, he knows more about that e-manage than anyone. Scalberts like the father in My Big Fat Greek Wedding w/ the windex. You could be like...uhh my car rattles over bumps...e-manage. I'm gettin bad gas mileage....e-manage. My dome light doesn't work...e-manage.

Originally posted by darrinb
what does scalberts intercooler cost??

Originally posted by scalbert
I don't sell them nor want to.

But they are available and easy to work with.