3.2 ---> 3.4 with supercharger

[drl911]

History - Some may have read my thread(s) a couple of years ago about mildly superchargering my '86 Carrera with nice results. PO owner had already "built" the engine with 964 cams, ARP bolts, headers, M&K 2in/2out exhaust and chipped to the tune of 229RWHP. The addition of the Vortech supercharger and DIY fabrication of intake plumbing, RRFPR (boost controlled pressure), MSD BTM (boost controlled retard), etc. lead to 324RWHP on the same dyno. Great fun in a dedicated 2300lb DE car!!!

Today - The tired engine currently has 192,000 miles on the odometer with about 50,000 of those with the PO mods (cam, etc) and about 15 DE weekends with my supercharger mods. It is now exhibiting what I believe to be excessive blow-by and causing excessive block pressures to the point the catch can in the air line back to the throttle body is seeing about 12oz of oil per DE weekend. I have not done a compression check nor have I been to the dyno in 2 years, but hp is in decline.

Future - I want to replace the piston/cylinders and perhaps go to 3.4 liters. I definitely want to keep the supercharger mildly boosted to 5~7psi. LNEngineering offers a wide variety compresson ratios for 3.2 ~ 3.4, including a 3.3 at 8.0:1 that seems ideal for my situation. Input / thoughts encouraged.....

Thanks,
Dan

[DSPTurtle]

Take a look at JE pistons and having your cylinders bored and plated. Might be more cost effective for you.

[Speed Buggy]

Bugatti Veyron transplant.

[drl911]

Originally Posted by DSPTurtle

Take a look at JE pistons and having your cylinders bored and plated. Might be more cost effective for you.

Thanks for the input.

If I pursue this option, can anyone suggest/recommend a shop in the Atlanta area that does this type of cylinder work?

[drl911]

As an additional data point, Patrick Motorsports confirmed to me this afternoon that Mahle does not currently offer a lower compression 3.2 or 3.4 piston/cylinder set. If I felt more confident running 9.5:1 or 9.8:1 compression with mild boost, I would probably pay the upcharge for the Mahle 3.4l set. Thoughts???

[Steam Driver]

Being formerly associated with Supercharging of Knoxville, I cannot recommend J&E pistons for supercharged applications. Mahle were the only ones we found would live any length of time under even low-boost applications.

[Spenny_b]

Originally Posted by Steam Driver

Being formerly associated with Supercharging of Knoxville, I cannot recommend J&E pistons for supercharged applications. Mahle were the only ones we found would live any length of time under even low-boost applications.

Interesting....the guy who I've been working with on my project here in the UK is also not a fan of JE, but is religious when it comes to Omega. Naturally, I'm using Omegas in my build (long story as to why), and knowing some of the projects that Fred and the guys @ Omega get involved with from F1 & MotoGP downwards, my trust is with them as well (e.g., every Ducati MotoGP and superbike for the last 20yrs has used Omega pistons).

Not wishing to start a holy-war or anything, but what wasn't so good with the JE's when used in a supercharged application?

[DSPTurtle]

I'd be interested in hearing the thoughts on JE also. I've talked to people who have said they had problems years ago, but recently, last couple of years, JE has been pretty darn good.
Send me a PM if you want to discuss getting your cylinders plated.

[JohnJL]

Well you can pretty much search and research my threads which did exactly this and has 10 years of tuning and revision experience. Happy to share my fuel and ignition maps, plumbing porting and other notes just ask.

I have 490 FTLBS AND 495HP at the wheels and a lot more available with another pulley and tuning.

[Steam Driver]

Re: the JE pistons and supercharging. Failed in the Dino. Various failures; ring lands, crowns, etc. usual stuff.

[KTL]

JE tends to get a bad rap for a few reasons. One was a forging failure that was also attributed to the use of tapered wall pins. I believe JE has since corrected that design. Another reason is some have chosen to use an off the shelf piston for an application that the shelf piston may not have been intended to serve. Point being is if you're doing something like this, it would be advisable to have a custom made piston. JE can do that.

[drl911]

Originally Posted by KTL

JE tends to get a bad rap for a few reasons. One was a forging failure that was also attributed to the use of tapered wall pins. I believe JE has since corrected that design. Another reason is some have chosen to use an off the shelf piston for an application that the shelf piston may not have been intended to serve. Point being is if you're doing something like this, it would be advisable to have a custom made piston. JE can do that.

I've read similar on internet.... makes sense.

So I may be rationalizing, but if I could purchase a LN Engineering "Nickies" kit intended for 930 - 3.3l @ 8.0:1 compression and run mild boost seems like it would match the design intent and be fine.

[sammyg2]

At 8 to 1 compression you wouldn't have to run mild boost.

Without an intercooler, 9.3 to 1 would be pretty much maxed out at 7 psig.
At 8 to 1 you could probably run 11 psig sans intercooler, but that's getting pretty hot.
With an intercooler and 8 to 1 you could easily run 1 bar (15 psig) or higher.

Remember when you drop the compression that far you are giving up a lot of torque. It's only worth it if you make it up with boost.

[drl911]

Originally Posted by sammyg2

At 8 to 1 compression you wouldn't have to run mild boost.

Without an intercooler, 9.3 to 1 would be pretty much maxed out at 7 psig.
At 8 to 1 you could probably run 11 psig sans intercooler, but that's getting pretty hot.
With an intercooler and 8 to 1 you could easily run 1 bar (15 psig) or higher.

Remember when you drop the compression that far you are giving up a lot of torque. It's only worth it if you make it up with boost.

Good info!

What's your opinion with Mahle kit 3.4l @ 9.8:1? Is 5 psi with intercooler doable (all of this is with single plugged)?

[drl911]

Anyone with factual confirmation that Mahle 98mm piston/cylinders intended for 930 application are straight bolt on for 3.2l NA engine.

[KTL]

930 3.3L case, rods & crank are same dimensions as 3.2L. So yes the 930 98mm P&C set will bolt right on to the 3.2

However I don't know if the cylinders are partly finned like 930 factory cylinders. I personally would want fully finned cylinders

[drl911]

Here is a pic of the set I am looking at buying. 3.3L 7.5:1 CR
Comments?

[drl911]

Originally Posted by KTL

930 3.3L case, rods & crank are same dimensions as 3.2L. So yes the 930 98mm P&C set will bolt right on to the 3.2

However I don't know if the cylinders are partly finned like 930 factory cylinders. I personally would want fully finned cylinders

The ad indicates fully finned. The part # cross references to '91~'92 turbo hence the CR of 7.5:1

Fitment still confirmed good for '86 3.2?

Thanks!!!

[KTL]

The '91-'92 Turbo uses the previous generation 930 case, which is the same as the 3.2 case. So the cylinder fitment into the 3.2 case will be the same.

[Tie Rod]

Originally Posted by drl911

As an additional data point, Patrick Motorsports confirmed to me this afternoon that Mahle does not currently offer a lower compression 3.2 or 3.4 piston/cylinder set. If I felt more confident running 9.5:1 or 9.8:1 compression with mild boost, I would probably pay the upcharge for the Mahle 3.4l set. Thoughts???

This is actually a sticking point for me (and others). I have a brand new set of Mahle 98mm P&C which are supposed to be Max Moritz style to put into my 3.2. In trying to quickly access my CR, I emailed Mahle Motorsports NA to get the dome volume specs on the pistons. I was told (still have email) that Mahle made two pistons from the 98P11 forging. One was 10mm tall and the other 9.3mm. My set measures at 9.3 and as I have found with others in the same boat, the CR is in the low 9's at best. I was told both work in a 3.2 Motronic Engine. I have not been able to find the answer as to what the two sets were made for. When I plug the supplied 10mm specs into the CR calculator, I get much closer to my desired 9.8to1.

Perhaps the 10mm are the Max Moritz style, but I don't know the difference per Mahle.

This is a point I will pursue to the end. I may just have a Low Compression set of Mahle P&C for sale.....