Where have the exotic 944 projects gone???

[sawood12]

Ok here's someting i've been pondering in my mind recently. What is the general feeling on aftermarket EMS systems like Motec and Wolf? I feel they have to be the best technical solution but are just very expensive which is why I guess most people on this forum that have completed big projects so far have not gone down that route. I just think that the flexibility that they can provide means you can tune the engine to modern day standards. In theory you can get rid of mapping altoghether and have every parameter of the engine contolled in a real time closed loop control system. E.G. you could have wideband O2 sensors for each cylinder with individual MAP and knock sensors for each cylinder, not to mention things like vario cam (if you were using a 968 head) so you could tune the cylinders individually for fueling and ignition in real time for every single revolution. I'd also like to see a wastegate electronically actuated and controlled by the EMS instead of a wastegate actuated by a pressure signal which would negate the need for any solenoids and pressure reducing valves - you can just programme your boost curves in the EMS. And of course in future if we would ever see a 944 with a variable vane turbo and direct fuel injection then a programmable EMS would greatly simplify the control interface. With all these modern devices fitted to the engine along with good closed loop control then 400bhp out of a 2.5ltr engine should be easy - Rick Cannell has already proved it is possible without alot of the bells and whistles i've mentioned here.

 

[Diver944]

Yes they are expensive and yes you have to install extra sensors to let the EMS know exactly where your engine is in it's cycle but ultimately it is the best way to go.

Rick already has the Wolf system, Fen has the Autronic and Nick has Motec fitted to his 968 Turbo. I'm not sure about the Wolf but the other two do control the boost level electronically - if you look at Fens graph on http://www.cannell.co.uk/944%20UK%20League.htm you can see that the boost climbs to 1.5 bar and is then held there as the EMS switches the wastegate on and off.

The Autronic has a 'learn' setting that Fen used to get the initial map but he did then need to fine tune it on the Dyno

 

[sawood12]

I'm pretty sure Rick uses his Wolf 3D to control boost as well.

What are the drawbacks of the alusil cylinders? Seems that Porsche stumbled on a really neat engineering solution when they developed alusil and I believe Mercedes and BMW also utilise the same process, but why on the large engine projects do people line the cylinders? Is it because you remove too much material from the block and weaken the cylinder walls? Seems to me that there are problems with liners and unless you get it right you are going to create more problems than you are solving.

 

[333pg333]

Scott, there's nothing wrong with Alusil at all. The only problem comes when you want to go up in capacity and when you bore the block you also run out of the Alusil itself. I think there was someone doing Alusil sleeves maybe?? Putting in metal sleeves is a very old modification and there's nothing really wrong with that in theory. You just have to ensure that all the components are going to work in concert. We were not supplied with the right information when we put our engines back together hence both cars were off the road AGAIN shortly afterwards. Mine lasted 4 days!!! With the stock Alusil lined cylinders and the Mahle pistons, they had very similar expansion rates. Hence the piston to wall clearance of something like 0.001mm I believe. Also the Alusil is relatively soft and prone to scoring. So they are great in many ways but so can sleeved motors be too.
Also from my understanding the EMS systems do require a fair bit of tuning and I don't believe that they have knock control, or at least the Motec doesn't. Of course this can be remedied but the ease and convenience of going with something like the Vitesse software and SMT6 was too tempting for me. I think ultimately the ems are better but good piggy-backs can get you pretty close in many cases.

 

[TTM]

ORIGINAL: 333pg333
We were not supplied with the right information when we put our engines back together hence both cars were off the road AGAIN shortly afterwards. Mine lasted 4 days!!! With the stock Alusil lined cylinders and the Mahle pistons, they had very similar expansion rates. Hence the piston to wall clearance of something like 0.001mm I believe.

What cylinder/piston clearance was used ?
The 968 WM states a clearance diameter of 0.02 mm.

 

[333pg333]

TTM, this was not a stock rebuild. We used Darton Mid Sleeves and JE pistons. The clearance used on my mechanic's car was the generic one supplied on the JE spec sheet of 0.004. He had all 4 pistons bind. We then went to 0.006 on mine and had one failure. As discussed previously, the JE's are highly expansive and need more room. Especially on a turbo car.

 

[sawood12]

I know that the Wolf System has knock control - there are two boxes, the Wolf EMS and the Safeguard knock control system, but looking at what people have achieved with the Vitesse Piggy back system i'm trying to understand what over and above benefits standalone EMS provides. Seems like it might be another case of the law of diminishing returns!

 

[TTM]

ORIGINAL: 333pg333
TTM, this was not a stock rebuild. We used Darton Mid Sleeves and JE pistons. The clearance used on my mechanic's car was the generic one supplied on the JE spec sheet of 0.004. He had all 4 pistons bind. We then went to 0.006 on mine and had one failure. As discussed previously, the JE's are highly expansive and need more room. Especially on a turbo car.

What clearance will you be using next ?

 

[333pg333]

We're not using JE's again. My mechanic is using Wossners at 0.006mm which is about double what they spec, and I am using some custom forged ones that are out of Argentina which are virtually like Mahles. Same material and clearances on some dry sleeved and Alusil motors that they're in, so I will probably go to 0.004mm. At this stage we don't care about a bit of 'cold slap' on startup. It's much warmer here in general anyway. We just don't want any seizing again, it's not a good feeling I can assure you.[]

 

[333pg333]

Just a quick one. The rolling road that you guys use, are those hp figures at the crank or at the wheels?

 

[Guest]

ORIGINAL: 333pg333

Tom, funny you should ask the same question I did about how you measure the clearance on a round object. However JE spec'd 0.004mm and this is measured from any side so it doesn't become 0.004mm x 2. With the liners you're using there may be a more compatible expansion rate with the pistons. The Mids are very thick and hard so not much movement from them. When this was coupled with the highly expansive JE's we ran into issues. After a bit of digging around it would seem that 0.0075mm is about where we would go if we were using JE's again. Well my mechanic has just done his re-re-assembly with Wossners at 0.006mm. I am going to be using some of Dave's custom forged pistons which have the same composition as Mahles. He has got his clearances down to 0.0012mm into dry sleeved or stock Alusil block. We are going out to approx. 0.004mm with these in the Mids and will live with a bit of cold startup slap and maybe a bit of premature ring wear at worst. It sure beats piston seizing!
PS If I had my time again I would do many things differently...[][][]

Hi Patrick,

I have been giving this some thought. Aluminium based Alloys expand a lot faster and further than steel. This would make sense in what happened to the JE Pistons with Darton Steel Sleeves. From cold the pistons would expand before the bores and hence the damage. I am certainly hoping that my JE Pistons do not expand faster than the Nikasil plated Alusil Bores. All will be revealed!!!

 

[nick_968]

Tom

The JE pistons and Nicasil bores should work fine as it has been done before, I think this is what Pauls car is running so as long as your clearances are right you should be fine.

 

[333pg333]

I agree with Nick. You should be fine Thommo but it will depend on the clearances set. With a treated bore or even a dry sleeve they will not only expand in concert with the piston, but they help to dissipate heat more than the thick MID sleeves. The Mids are good from the point of view that when they suffer damage like mine then to replace or repair is generally pretty simple. Again it's a matter of getting the correct clearance and the best piston to suit. There are varied opinions of JE pistons I must say. Since going through this I have been in contact with quite a few people not the least one of the patent holders of the Darton Mid system and he uses JE's in his own builds. However he uses these mostly on large n/a V8's and it was he who eventually suggested that JE's in the MIDs needed 0.0075" clearance. We have since heard similar numbers from others with experience with JE's. Unfortunately there are far fewer people with the MID's in our cars than we first were told about so we have felt like the Guinea Pigs to a degree.[]
Oh and any idea as to the power readings by the dyno you guys prefer whether it's at the crank or the wheels?
Thanks.

 

[Diver944]

The Dyno Dynamics dyno at Weltmeister that we use gives a calculated flywheel HP figure after it has taken a reading at the wheels. They will give you a graph for the wheel HP if you ask for it but it's not generally the way it's done over here.

Because we all use the same dyno and because it has demonstrated time and time again to be accurate and repeatable within a few percent, we are more than happy to use it to make comparisons between the cars over here. Obviously you can't really use it to compare cars around the world, the only true way to do that is to remove the engine and stick it on an engine dyno (and I dont think any of us have the budget to keep doing that [] )

 

[333pg333]

Yes that's true Paul. It does seem as if there is a general belief that the US dyno's are somehow a bit optomistic so I agree that at least you guys have a good system of control with the Welt. It would be nice if there was some sort of formula, system, thumbnail guide as to be able to do comparisons across the globe. I hope to get mine to the dyno in the next few months so it will be interesting to compare not only hp figures but the dyno itself.

 

[George Elliott]

Patrick, There is a world-wide standard - the rollers of truth[].....I also take some of the USA claims with a bucket of salt.

Sorry to read of the seizing you have experienced, I notice ref made to the clearance on the bores, sometimes in metric and the last ref in Imperial. The 0.004mm ref is so tight it would not run. The seven and a half thou is more likely to be right IMO.

I only mention it because if your machine shop mix up the two then.....Also if the clearance is 0.0075" then the bore diameter is 0.015" bigger than the piston? 15 thou is about 0.04mm.

(I once had a mechanic mix up lb/ft and N/m of torque.)[>:]

George

944t
964

 

[sawood12]

I do seem to remember Alan at Weltmiester explaining that he has optimised his dyno specifically for Suburu's and Porsche's as he has alot of experience with those cars so is not simply using standard assumptions to back-calculate flywheel HP and he reckoned his dyno was pretty accurate on those cars. The Weltmiester website advertises that they have an engine dyno as well so I can only assume that at some stage he has done the back-to-back engine dyno to rolling road comparison at some stage.

 

[333pg333]

ORIGINAL: George Elliott

Patrick, There is a world-wide standard - the rollers of truth[].....I also take some of the USA claims with a bucket of salt.

Sorry to read of the seizing you have experienced, I notice ref made to the clearance on the bores, sometimes in metric and the last ref in Imperial. The 0.004mm ref is so tight it would not run. The seven and a half thou is more likely to be right IMO.

I only mention it because if your machine shop mix up the two then.....Also if the clearance is 0.0075" then the bore diameter is 0.015" bigger than the piston? 15 thou is about 0.04mm.

(I once had a mechanic mix up lb/ft and N/m of torque.)[>:]

George

944t
964

Whoops, you're right there George I did mix up my " with my mm's. It should be reading ". That's what happens when you live in a metric country and deal with others that are still using Imperial. I grew up using Imperial so I have no excuses.

 

[George Elliott]

Patrick
No bother - hope the rebuild goes well.
George

(Good to see you ain't got a 66" Throttle body with a 3mm exhaust[8|])

 

[333pg333]

Haha that's for sure George. It seems like there's more hurdles yet to negotiate. I now need to get a few people involved in my build on the same page as one another before we finally settle on the remaining components and process'. If someone had have told me when I bought the car back in Feb '06 that I would be off the road from Nov '06 to at least July '07 and have spent way over what I paid for the car I would have had to seriously consider what my options were. I keep telling myself that all will be well once rebuilt and all the waiting and lack of correct information put behind us. I just hope that's true. I also hope Paul is back on the road asap as I don't envy his next few months.