pete944

There's a big gray area in exactly what's needed to convert a 968 or 944S2 to a heavy breather.
How about using this thread for anyone who has done it to list what's needed, where to get it, what works the best, etc.
This is open to all the builders like Anderson Motorworks, Technodyne, Jon Milledge, Powerhaus, etc., and anyone who has done a successful, quality conversion.

What everyone seems to want to know are things like:

What size and brand of piston?
What size and brand of connecting rod?
Which 951 exhaust parts will work?
Can the stock DME be retained?
What head/flywheel combinations work best?
What is the optimum compression ratio?
Does Mahle make a low compression piston for 16 valve heads?
Does anybody?
What modifications need to be done to the intake manifold?
MAP or MAF?
What's the best way to mount an intercooler in a 968?
Etc., etc.

How about it? Can we make a nice shopping list here?

alberto1

A lot of the knowledge you are asking came after a lot of effort in time and money. I will be surprise if any of these tuners will provide the details of there research for free for everyone to copy. Just ask Raj to give you all his secrets. It would not be fair to Raj. Anyway, if anyone want to let us know, be our guest!!!

Angel

pete944

I don't think any of the questions I posed are or should be 'secret'. I've heard differing answers to all of the above questions. I plan to do this within the next few years and I'm not going to ship my car across the country to a tuner/shop to do it.
I just want to know what works so I can begin stockpiling the parts.

Jay Wellwood

This sounds like a good idea.

Reaping more power out a Porsche seems to always be a challenge. As with the 968 Turbo project, alot of head scratching is involved. For those that have completed the journey - sucessfully, I too, am interested.

Alas though, attaining the knowlege and then sharing can sometimes be a difficult thing to do. Over on the 928 board, there is alot of talk concerning what is required to 'stroke' a 928 motor. At least 5 motors are in progress at this time that I know of. Of the 'big 3' 928 parts vendors, 2 are known to have completed this project - 1 shares willingly - although he's not a mechanic but is mechanically inclined. The other is a mechanic, but will not share the information...as it's not in his 'business interest'.

John Anderson

To start, it really depends on what the customers want, and what they are willing to invest in. For example, Trevor wanted a low cost low boost aplication that would give him an honest increase in HP withought affecting the looks of the engine bay. So for him we started with his block, kept the compression stock, kept stock rods. We made the intake manifold using the 951 intake plenum mated to the 968 runners..to do this, one of the runners had to have an extension tube added to get the angle and fit right. We use a 951 throttle body. 951 exhaust system, with some slight welding to get the flanges to match up. Timing and fuel are managed with a custom chip and adjustable FPR. The intake is stock, using the stock box and MAF sensor in its original location with mods to convert them to work. We tapped the upper balance shaft housing to get a 951 turbo oil feed line in. We used the water lines that feed the stock throttle to feed the turbop on one side and the other side went to the water pump, so no cutting of any water lines was needed. THere is no intercooler on his car, its direct from the turbo, thru a pipe to the throttle. He has not blown a head gasket, or had any failures since this was completed about a year ago. He makes an honest 70HP gain at the wheels as measured on the Dyno Jet. Runs on pump gas. Vario Cam is intact.

The S2 conversion uses an intercooler, garret turbo, same exhaust plumbing, same intake manifold , well..its an S2 with the 951 plenum. 951 throttle body, 951 exhaust, Pauter rods (shortened to make 9:1 compression), stock pistons, same oil plumbing, intake wwas removed and replaced with an MAF kit using the ARCII to adjust fuel, stock chips, adjustable FPR, air/fuel gauge..most everything else is the same as the 968 above.

Does this help?

pete944

Thanks John, that does help.
Did the S2 use the 951 DME & KLR? I'm guessing that the answer is no.
How much power did it make and at what boost level?

John Anderson

to date, our best Hp is 310 rear wheel, with a KK K26, but that little turbo just runs out of breath and boost level was pretthy high, too high to be able to last...we are using the stock DME on both cars. THe change out in computers mean a ton of harness work. We have just added the big garret to the S2, and are installing Big Reds, as soon as we get this stage out of the way, we will dyno tune it and tell about the results. I'm not looking for peak HP numbers, so you most likely will see a solid 340hp at the wheels. We will shoot for this while trying to keep boost under 1 bar.

Take Care

pete944

That's exactly the ballpark I'm shooting for. I'm hoping for 320-350 hp at 1 bar from my S2 when all is said and done.
I want to keep it simple to start with but have the option of upgrading in the future.

PorscheG96

Great info, John!

pete944

Thanks again John.
What about injectors? Will stock S2 injectors work ok with a similar combination to what you laid out?

John Anderson

We went to Aftermarket 52lb injectors on the S2, its getting pushed a tad harder that the 968 of Trevors. Trevor retained his stock injectors.

I saw that Chris white has posted about methods of doing this mod also. He and I have a different aproach. I have learned to keep it simple. Use as few aftermarket parts as possible to achieve the goal and try to avoid the urge to over engineer anything. Unless you have the time/resources and the customer has patience unlike a mortal, there is very little chance to test a new idea thoroughly before delivering the car. Stand alone has proven to be such an animal with me. First, After turboing many NA cars, 944's, S2's and 968, from stock engines to big bore blocks...I have found that managing fuel and timing with a solution that retains the stock computer has proven to be a very solid solution. I also do not like the idea of a customer being married to the dyno at a cost of 2000.00+ on initial tuning, or even high dollar visits to the dyno after making other changes down the road...turbo's cams etc etc.

For example. We have a car here that was built by another tuner, it was supercharged and a 100% gutted track car. Since getting the car, we have taken many steps to try and get it reliable and keep in on the track. First we got rid of the SC system, and rebuilt the moroe. Its sleeved using JE pistons and Stock forged rods. 2.8 liters. 9:1 compression. We had the unichip tuned for the turbo (2300.00US to tune on the dyno). Still failed on the track after a few laps. Next Step, ditch the Unichip, to many problems trying to tune for wide open throttle (infact, a tuner will only tune the part throttle map on this system at times), we installed a stock 951 dme klr with custom Steve R chip. Ran better, lasted longer, but still had issues with head lifting. Next step. remove the Raceware head hardware and install stock hardware. The raceware is a non stretch stud which will not keep a set when torqued. The stock studs will hold better as they stretch.

I bring up that story to tel;l you how at times, you really can't beat what the factory has done, you can cheat it, build on it, but its not always best to replace it.

We are going to the track this weekend with a couple of our cars, one is a factory 2.7 liter block that had the pistons shaved, forged rods inserted, and turbo'd. Stock computer, stock chip, with an adjustable FPR to manage things. We'll run race gas at the track, but on the street, the customer runs pump gas. A very simple solution, and this weekend will see how it acts when pushed to the limit.


My way is not the only way, but it works :-)

Take Care

pete944

Thanks again John. This discussion is helping me out. I don't want to re-invent the wheel, I just want it to roll a little faster.

Chris posted this in the thread on the turbo board:
"There are no pistons available for use in the stock type (non sleeved) cylinder and the 16v head so the block will need to be sleeved. JE makes a nice piston for the center fire 16v head."

You said that you used stock pistons on the S2 with shorter rods. Did you have to modify the pistons at all?

John Anderson

No we did not modify the pistons. The shorter rods allowed the lower compression ratio. I know about the "squish" area, but for this customer on this car, it was the best option.

Take Care

mslovak1

John,

I have spoken with you on the phone pertaining to this, and always enjoy your input!

For turbo'ing the 16v motor:
If all costs were the same, would you block and sleeve a motor and use turbo pistons. Or , would you stick to the method you mention above.

What are some of the pro's and con's of either, and do some of these outweigh others?

M

Jay Wellwood

btw - congrats to both John and Trevor for the article in Excellence!