I'm wondering about some mods and am thinking about M112 NA engine family. Following LantanaTX's V-8 conversion, I was wondering about swapping engines. The electronic issues are daunting though. By modifing or rebuilding the existing V-6 these problems would be avoided.



Following Infinite's and many others posting, I am thinking about a turbo system for a NA engine. I am thinking about a STS system. Before anybody jumps up and says it won't work I have some considerations.


The STS design nearly negates a intercooler. The heat factor is in another area, away from under the hood and simpler installation



I feel that in the NA engine stock configuration the compression is too high for the addition of a forced induction sysytem. To put it simply, forced induction increases compression. Starting at 10:1 ratio is a bit much. The engine doesn't care how the intake charge is compressed, just that it is compressed. How many head bolts per cylinder is there? The more the head bolts the greater clamping force for the head gaskets to seal. Studs also have greater sealing by virtue of their depth in the block.


Compression is the product of many factors but the easiest to control, from a manufacturing standpoint, is the piston design and the cylinder head combustion chamber volume / design. I was hoping that someone might have some pictures or specs of the SRT / AMG pistons and cylinder heads to compair to NA pistons and cylinder heads. Mostly manufactures change pistons for a forced induction engine. Many companies make custom pistons at reasonable prices. I think the heads are the same. I feel like the key is the pistons.


I considered a swap to the 3.7 used in the ML350 and S350.

1. In compairing our 3.2 to the 3.7 the 3.7 is about 7.1mm larger bore with the same stroke as the 3.2.
2. M-Benz rates the 3.7 at 235hp and 254 ftlbs of torque versus the 3.2's 215hp and 232 ftlbs of torque.
3. The 3.7 is 20hp and 22ftlbs higher, this on it's own is not worth a swap.
4. The 3.2 can obviously exceed this with tuning.

If you have any other suggestions, I welcome any and all comments or ideas.

 

I like the idea of an STS rear mounted turbo system, and I agree with you. I think that is a better route than an engine swap.

 

why not an engine swap?? I understand the integrity and fact the car is so unique with its MB/chrysler heritage. but why not do an entire engine/transmission swap??
Hinsonsupercars.com are putting LSX engines in rx7's, 350z's, 240's....
It can be done...

 

I like the swaps and think they offer great ingunity and problem solving. I also love street rods for the same reasons plus some excellent craftsmanship. But, they arn't my style, for this car. I also have a 400ci big block '76 Duster bracket car. These cars never came out with a big block but it was such a simple and cost effective approach. Also when I first envisioned the car (Duster) it was to be set up differently. I am hoping maintain driveability that I have grown to enjoy. The days of driving around with a big cam thumping are pretty much over for me.

 

the problem with the rear mount is ground clearance.
Theres no way to run the intercooler piping under the car without it hanging down.

I think i've found a way for intercooler piping to run in the transmission tunnel but have to look into it.

10:1 is perfectly normal, I've boosted motors as high as 13.5:1 without issue
Our motors have forged internals, and the domes of the pistons are iron coated, meaning they can take higher combustion pressure and temperature, the iron coating extends to the first ringland which means there should be few issues there.

The srt motor is virtually identical, only difference is the compression is down a point.

You can actually make more power with 10:1 vs 9:1. The NA motor has 2.8% better thermal efficiency than the srt motor, meaning with proper tuning you can make more power per lb of boost.

Im looking into a rear mount setup on my car, as a standard turbo setup is just too labor and cost prohibitive for the gains.

 

I was also considering the ground clearance issues. I believe the installations are usually in the muffler area but, could maybe moved into the resonator area whichever would be the best fit and most clearance.


Another concern is that the air intake is under the car in the dirt and debris. A shield or bit of tubing might work to deflect the larger items.


In looking at the parts catalogs on some of the dealer web sites, it shows that the SRT crankshaft, rods and pistons are different part numbers from the NA parts. I am wondering what the differences are, I think it would be safe to say they would be designed to deal with the stresses of a supercharged engine better. The crankshaft maybe designed to deal with the added stress of driving the supercharger.


The information concerning the pistons is a great help. Most modern pistons are made of aluminum. I can see that the iron coating would make a huge difference.


I am thinking that with added compression, supplied by the turbo (boost), comes added heat. Since the turbo does not create boost all the time in a street driven vehicle the decrease in compression would allow the engine to run cooler in an off boost situation. I'm not sure how to put this but, one thing noted in our vehicles is they run at a high temp. This may be built in for emissions and / or mileage but the cars run much better cooler. Higher compression ratios also create higher stress so, in an off boost condition the engine is under less stress. As the boost builds the compression will go up in the engine anyway.


I have a long commute to work and one of my favorite things is to mull over ideas like this, as I drive. Is there anything I haven't considered? That's what I enjoy so much about this forum the chance to work out ideas.

 

the pistons are different part numbers, since they are different.
the crankshaft has a different bolt pattern since the automatic flex plate and maunal flywheel have different bolt patters (dont know why)
the rods probably have bigger rod bolts, but are the same otherwise


compression doesnt matter when it comes to operating temps, the combustion chamber runs at the same temperature.
Theres space for the turbo itself up out of the way, as well as the exhaust piping. Most people just get lazy when it comes to charge piping and they run it straight under the car.

 

I see the point as to the compression and heat. I'm not sure what I was thinking. I guess that I was trying to equate heat and stress. I've noticed that the NA and SRT seem to use the same head gasket. I haven't been able to find out about the head bolts. It appears that there are four bolts per cylinder. Piston rings are also different.


In the catalogs the crank differences are listed as supercharged (SC) or NA. I'm not seeing a difference for manual / auto. The bearings seem to be the same including the thrust. The crank gear appears the same. The vibration dampner is listed as SC or NA. I'm sourcing a couple online catalogs so they might not be exactly accurate.


I wonder how high the boost goes on the SRT. I'm thinking that the SRT has a 9:1 compression ratio, is that correct? The turbo could be limited for the NA with the waste gate.

 

the srt pistons might have a thicker first ringland, the na motors cranks are the same manual vs auto. the srt uses a different flywheel bolt pattern, probably because they might use a different flexplate/torque converter

the crank dampeners are different because the srt has a different diameter for supercharger rotation.

 

If the 3.2 goes or i get bored with it. I was rolling around the idea of the buick 3.8 v6. Those turbo buicks are mean.

 

my neighbor had an 86 grand national i almost bought, thing was nasty.. 680rwhp. It was going to be mine for only 10k, nothing wrong with the car just couldnt get the money together fast enough.

Honestly if the motor in my car let go, if i were to keep this car for awhile I'd simply buy a 2jz and be done with it

 

Hello guys n gals! First off, I have been following all this turbo stuff for the N/A XF since buying mine. I wanted to just throw out a little bit of information that has been bugging me since seeing all the differences posted in the 3.2L N/A v the 3.2L SRT. Has anyone actually set the different parts from each side by side and looked into the physical/metalurgical differences between the two? The reason I ask, I had a 3.8L in my 89 Buick Park Avenue that needed two of the three coil packs. The local Buick dealership looked up the price for the Park Avenus ones, and they were over $110.00 each! I went home and called the same dealership and asked for the coil pack price for the 3.8L LeSabre (different part number) and to my surprise, they were just over $60.00 each. As a point worth noting, the coil packs are electrically and mechanically the same. They both swap between each other and btw the generic ones were almost half the cost of the one for the LeSabre. Point I am making, just because it is a different part number, is there truely any difference in them?

Has anyone put the S/C from the SRT on the N/A? If they did (understanding a few mods in brackets/heads/routings), how did it work? Anyway, I'll understand being flamed like crazy if it's already been done and researched already, its just I cannot get those coil packs being the same except the part number and price for the 'higher class' Buick. Peace-Out!

 

the blocks are identical, the front covers are different.
Crank, rods, headgaskets, heads, etc are all the same.
The crank flange just has a different bolt pattern.
Pistons are a point down in compression, everything else is the same

 

will somebody please just boost this engine and tell us what happens? I'm desperate to do this.