924Board.org

[Mike9311]

Ok, at least for a small cylinder 86.5 the whole shift your head 1mm back doesn't work

Exhaust side of the chamber is already at the cylinder edge. In one case it was already past the edge. Look at the top of the pic to see how this is at the edge limit. Don't want to mess with cylinder sealing between cylinder either. I would do this trick though with larger pistons like 87.5+

There is a small amount though left on the intake side to carefully carry the chamber out to help nozzle the chamber right up to the cylinder with some careful 'bowl blending'

Will still be shifting the Intake valve itself. I modeled as much as 2mm but I don't really like the contact at the tappet. It does help though that there is a large area valve stem cap but I still think it will be less



I'll scribe the bowl limit like I am doing in this pic below on a Duc head. Then blend out to that scribed line.


_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Cedric]

Joakim did offset his cylinderhead if I remember correctly, but i think he have 87,5+ bores on the other hand. it do look tight towards the wall for sure.
_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[Joakim]

[Mike9311]

That's the information I have too on Joakim. From what info I have, its a 1mm shift.

I was hoping to 1mm shift the guide and 1mm shift the head for a 2mm total shift.

The max shift I have seen in a guide is 0.085" or just over 2mm. I feel like this is a lot for a guide shift.

A UK mini cooper example I found is 0.05 or 1.25mm. I might try 1.5mm if there is enough material at the top of the guide for an offset guide seal seat. This is the other end of the problem. The valve stem seal boss or seating area needs to be round and I am pushing that boundry.

At least with a 1mm offset I am ok and with a 42mm valve I am like the stock 40mm vs the cylinder wall
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Cedric]

I can barely se it being worth all the effort for offsetting the valve 1mm needing all these special parts, especially not on a turbocharged engine, and non competitive. But it all depends on how much fun you want to have building it i guess
_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[Cedric]

[Mike9311]

The years do stack up

It is crazy but I seem to like the journey when I actually do something.
I have invested in tooling. Too much already but again I like this stuff and have more 924's to build plus other cars. This doesn't include what I am building to fixture the head


Update (formerly Dan's CS): Trying not to do too much engine bay clean up but it needs it.

As stated previously I am putting a temporary motor into the car because I thought I would be quick but haven't been obviously. I wasted some time trying something else and then told myself to calm down and not rush. Hence the replacement motor. The bottom end is ready and its essentially stock S2. I did skim the block to prep for a Cometic.

What might be interesting is that I plan on running a stock cam (unless I change my mind in the next couple of months) on this head I am building here. Hopefully fueling will be FrankenCIS but no other real changes. All FrankenCIS parts are in hand except fuel lines and however I plan on mounting. Might do larger radiator for the WCTMIC that came on the car but that can wait of course

Oh, I forgot, the custom turbo too. The one were I modified the housing to accept a billet HF 7+7 2667 compressor. Started that in the thread link here for anyone that cares. I know you saw it

https://www.924board.org/viewtopic.php?t=40119&postdays=0&postorder=asc&start=45

You have me wanting to put that baffle into the oil pan or else that would be bolted on already. Some stuff is just loosely sitting on the block but the oil pump and new water pump are installed.

I really want this car on the road in the Spring so I am pushing hard now

Edit: forgot to mention the UK offset guide is different. They sleeve the head with a piece of iron (iron head) and this iron is offset so it accepts a regular guide. They do it to the Exhaust valve to provide room for the larger intake valve.






_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Mike9311]

This head will be flow tested as well. Just invested in a bench set up traceable to NIST. Velocity testing can be added down the road. Just want to get set up and comfortable first

Will also be building cylinder adapters for any likely combo. First up up course is 86,5 in stock location since this is how this first head is being used.

Started modeling the fixture uprights. I am thinking another week lost to fixture improvement is better than me trying to rig something with what I built so far.
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Cedric]

Looks good, i do hope you get it all together for the spring. How come you dont go to a more aggressive cam?

Velocity measurment is fairly simple, just a pitot tube and differential pressure meter, Quite important if you want to fiddle with the ports. Will be interesting to see some data!

Are you aiming for track driving with very wide sticky tyres? If not then dont bother with the baffle, they are pretty good in standard form.

I got it welded at the shop who did the machine and assmelby work of the bottom end and cylinder head. He said it was a pig to weld due to the impurities in the aluminium, even though it went through a parts celaner machine, baked etc.


_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[Mike9311]

Nice! I know how your welder feels. Its been interesting welding a head I am attempting to save (not this one) and the torque tube. You want to make the weld look like something from Instagram but then all this strange stuff floats up out of the weld. On the other head, I actually figured out that small corrosion spots around water jacket holes on the head tend to go deeper under the better parts of the head potentially weakening the areas you think would be good. They look like termite tunnels. It was surprising and not surprising all at once

I was actually thinking about you Cedric, when I thought about the stock cam. This way I would have one less variable when looking at power levels when it gets tested. The plan right now is FrankenCIS which will require a tune. What is nice is that there is a shop that can dyno tune a few miles from me. They fly a guy in who spends days tuning appointments. They know megasquirt so the FrankenCIS should appear no different on their end. I have literally everything but the lines

My other excuse is that the camshafts I have are bad. I thought I could re-use the Stage one Integral but I don't like the looks of the lobe tips especially on cyl 4. I also have what appears to be a Webcam grind that looks too radical for a Turbo. This was that pic I posted on Insta with the lobe scans on top of each other. I was looking at everything I had to see what I could use. The only negative is the larger stock lobe will leave my valve length shorter if I switch later to a regrind with a smaller base circle. Would need thicker lash caps when switching but I could make those. Its a bridge I can cross when needed. No need to think about it now

Would actually be neat to grind a cam based on my eventual flow numbers. I want to share whatever data I get too especially with you etc. I have untouched heads that I want to check. The head I am doing now was ported but poorly and then I have the original CS head.

The Club Sport came with two sets of wheels. One for Street duty and one for Track. If the car runs nice I plan on track days for sure. There is a super nice track near me that I have been to several times and another couple north of me. Would love to get some pics of the CS at Road America in Elkhart Lake Wisconsin
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[safe]

[Mike9311]

[Cedric]

Not a bad idea to start out with the standard cam, you will still probably be in the 250+hp area if you want, and that feels pretty quick in these cars. Especially when the car is more or less untested on track there is alot of stuff to be sorted out first. Like oil and water cooling, boost cooling, brakes, suspension, alignment, engine tuning, etc. Most which isnt really possible to sort out on the roads, no matter how hard you try. Do you intend to do frankecis with the stock 931 setup? Im very interested how far that one could be pushed.

Road america is seriously long and fast, much longer and faster than what Im used to. Lets hope you get there soon
_________________
1980 924 Turbo
www.instagram.com/garagecedric/

[Mike9311]

I will admit that, after seeing how close the dyno numbers were for CarreraRSR and Lildude4life, I have been wondering where my numbers would fall in comparison. They really approached this from two different angles. Old school vs new school both in physical parts and fueling.

I did go all in regarding the FrankenCIS at least with buying parts. Overkill at the 250HP level for sure. I have the Merc V8 CIS and all the other parts. Of course I want to see how far I can push but at the same time I want start slow. By slow I mean, I am even pulling the Euro 10psi spring and replacing with a US S1 spring for now. Part of the other reason was that The CS has the GTS lights so I have been wanting to add other GTS additions like this merc CIS and the GTS interior gauge center.

The replacement 2.0 motor has a stock bottom end that looks decent but that remains to be seen once it fires up. So I am starting there. Then I want to work through everything and make sure its all functioning as it should. Data, data, data... Eventually a version of the original 2.2L will go back into the car with the knowledge that the supporting components are good.

The reason being this car has me spooked. The story hasn't really been told here but something happened to the engine that has been under debate locally (gatherings that include Dan) to the point that we don't even bring it up anymore since we really can't know all the variables given how many people drove the car including myself before I bought it. In my day job I am really good at figuring out why things fail and its part of what I do. Sometimes though I need input though to round out the whole picture. With the CS, we just don't have the full story and I don't think we ever will. We have some ideas and just left them at that...No need anymore to beat a dead horse

If I posted a picture of a CS piston you would know why I am spooked. Correct AFR and 10PSI shouldn't have done what it did so the mystery remains. My 80 S1 was fine when I fed it 1bar from time to time but mostly 12-13 max since above that did nearly nothing. I pulled the head on that car and it was all good.

Edit: Almost did RA on a bike but failed to get it together the night before. Went anyway to watch my friends. Bike ran a few days later. Maybe its good I didn't Its a bit crazy. anyway...


This is the Merc CIS-E unit I have




_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car

[Cedric]

Well, a wideband is only showing the average of all four cylinders, one can easily run leaner than the others without noticing it. Testing all 4 cylinders fuelling help, or some kind of knock detection. As long as it doesnt knock i think that bottom end will work fine,if it does it might create a hole in a piston

So you went for the big one, then you will have fuel enough for pushing that turbo far enough , even though i never recommend anyone to bottom out a turbo. Or maybe even fuel enough for e85, if you want to go wild. But the long term durability of the fuel distributor and e85 need to be researched.
_________________
1980 924 Turbo
www.instagram.com/garagecedric/