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My 924 Turbo, data logging AFRs
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CÚdric  



Joined: 27 Aug 2004
Posts: 1884
Location: Sweden

PostPosted: Mon Aug 05, 2019 8:34 pm    Post subject: Reply with quote

Hi guys.

The corrosion we are talking about is the large grey area in the middle of the cylinder. Its definitely a re-bore as i can feel the irregularities in the cylinder wall. But I will run it as it is for now, just do the cylinder head.

I could actually measure blow by flow with the help from a blow by meter from work, they are pretty nice 0-5v units. Will start by hooking up the purolator outlet to a bottle and see how much oil carry over i get. There were some traces in the lower CIS unit (s2 routing), but nothing exessive.

I have a spare head, with some polished ports, new guides etc, but its in one million pieces, i think that head will hop on the new engine block when time comes. And then i can be more serious with recutting valve seats etc on that head.

Thanks for the offer about repackaing the ARPs, they really are much cheaper over there, i will dig around a bit regarding the shipping and i will come back. The cometic had a month lead time, so no stress

I would most likely not want to go to a fully flat piston, i might want to reduce squish area a little bit, but still want to retain a certain amount not to kill the combustion flame speed. this car needs driveability aswell, it wont be a boost monster 8:1 is probably a good level, i will go there now with the MLS i have ordered, so steppin down from 8:5, just to get a bit more margin.

I think Joakim and his 450hp engine uses JE pistons, but my memory is a bit hazy.
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1769
Location: MI

PostPosted: Tue Aug 06, 2019 1:42 am    Post subject: Reply with quote

The weak rim on the dished pistons disturbes me and I'd like to go non-interference if I could.. Machining a dish also sounds expensive, especially one that includes valve pockets, and then that sounds like a whole lot of math to figure out CR..

I don't even think they need to be light, just super strong and det resistant..

Car don't make no power when it ain't in boost anyway and doesn't rev either unless you want to do rods, pistons, lifter buckets, and maybe valve springs..

But I'm at 7.5:1 compression right now so that probably doesn't help much either..

How bad do you think loosing the squish area would really effect it?
The NA doesn't have any squish and makes 120HP with no boost..

You ever drive an NA? Do you think they have poor drivability due to no squish?
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chuck21401  



Joined: 20 Feb 2005
Posts: 133
Location: Annapolis, MD

PostPosted: Mon Sep 16, 2019 12:21 am    Post subject: Reply with quote

I have one of the AEM AFR gauges in my car.

I was reading the installation manual and looks like the gauge can be connected to a RS 232 (DB9) cable and then to a laptop. What else would I need? RS 232 to USB port adapter?

https://www.aemelectronics.com/files/instructions/30-4110%20Digital%20Wideband%20UEGO%20Gauge.pdf


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CÚdric  



Joined: 27 Aug 2004
Posts: 1884
Location: Sweden

PostPosted: Wed Oct 09, 2019 8:14 pm    Post subject: Reply with quote

The head is finally back, they were very slow unfortunately. But now its skimmed, 4 of the valves didnt pass their seal test, so machined seats etc, new valve seals are in aswell (I found one of them in the sump as I mentioned before), and some other small stuff.

ARPs are in, Cometic MLS is here, to bad i hadnt ordered nuts bolts and gaskets, so that will have to wait until next week. The plan is to put it back as I took it out, with the manifolds and everything still attached.

Pic of cylinderhead with a link, sorry, i have better upload serivce at the moment..
[img]https://www.bildtagg.se/file/thumb/ebzlqv6mc9zo4cz06ms8himz[/img]
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safe  



Joined: 18 Mar 2017
Posts: 80
Location: Sweden

PostPosted: Wed Oct 09, 2019 9:00 pm    Post subject: Reply with quote

CÚdric wrote:
The head is finally back, they were very slow unfortunately. But now its skimmed, 4 of the valves didnt pass their seal test, so machined seats etc, new valve seals are in aswell (I found one of them in the sump as I mentioned before), and some other small stuff.

ARPs are in, Cometic MLS is here, to bad i hadnt ordered nuts bolts and gaskets, so that will have to wait until next week. The plan is to put it back as I took it out, with the manifolds and everything still attached.

Pic of cylinderhead with a link, sorry, i have better upload serivce at the moment..
[img]https://www.bildtagg.se/file/thumb/ebzlqv6mc9zo4cz06ms8himz[/img]


I just read up on MLS gaskets. It seams it needs very flat and really nice and smooth surfaces.
Somewhere between "can't feel scratches with finger nails" and polished.
How have you prepped the block?
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CÚdric  



Joined: 27 Aug 2004
Posts: 1884
Location: Sweden

PostPosted: Wed Oct 09, 2019 9:51 pm    Post subject: Reply with quote

safe wrote:
CÚdric wrote:
The head is finally back, they were very slow unfortunately. But now its skimmed, 4 of the valves didnt pass their seal test, so machined seats etc, new valve seals are in aswell (I found one of them in the sump as I mentioned before), and some other small stuff.

ARPs are in, Cometic MLS is here, to bad i hadnt ordered nuts bolts and gaskets, so that will have to wait until next week. The plan is to put it back as I took it out, with the manifolds and everything still attached.

Pic of cylinderhead with a link, sorry, i have better upload serivce at the moment..
[img]https://www.bildtagg.se/file/thumb/ebzlqv6mc9zo4cz06ms8himz[/img]


I just read up on MLS gaskets. It seams it needs very flat and really nice and smooth surfaces.
Somewhere between "can't feel scratches with finger nails" and polished.
How have you prepped the block?


I havent done anything with the block, i just havent had the time/energy to even look at the surface. I will try to clean of the surface and see how it looks like. Ive heard both about the surface for MLS, some say its easy some says it needy. The block wont come out, so i will have to do with manual methods to get it good enough. Any recommendations on products or methods to get the old stuff of the surface?
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safe  



Joined: 18 Mar 2017
Posts: 80
Location: Sweden

PostPosted: Wed Oct 09, 2019 10:12 pm    Post subject: Reply with quote

CÚdric wrote:
safe wrote:
CÚdric wrote:
The head is finally back, they were very slow unfortunately. But now its skimmed, 4 of the valves didnt pass their seal test, so machined seats etc, new valve seals are in aswell (I found one of them in the sump as I mentioned before), and some other small stuff.

ARPs are in, Cometic MLS is here, to bad i hadnt ordered nuts bolts and gaskets, so that will have to wait until next week. The plan is to put it back as I took it out, with the manifolds and everything still attached.

Pic of cylinderhead with a link, sorry, i have better upload serivce at the moment..
[img]https://www.bildtagg.se/file/thumb/ebzlqv6mc9zo4cz06ms8himz[/img]


I just read up on MLS gaskets. It seams it needs very flat and really nice and smooth surfaces.
Somewhere between "can't feel scratches with finger nails" and polished.
How have you prepped the block?


I havent done anything with the block, i just havent had the time/energy to even look at the surface. I will try to clean of the surface and see how it looks like. Ive heard both about the surface for MLS, some say its easy some says it needy. The block wont come out, so i will have to do with manual methods to get it good enough. Any recommendations on products or methods to get the old stuff of the surface?


I was thinking of using a (new) whetstone to get it smooth, but if someone has a good solution how to not get crap down into the water and oil passages I'm all ear. Or another method al together...
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Carrera RSR  



Joined: 08 Jan 2010
Posts: 1807
Location: Somerset, UK

PostPosted: Thu Oct 10, 2019 4:44 am    Post subject: Reply with quote

I read that the MLS needed a 50 roughness average. I have no idea what that looked like. I asked my machine shop to deal with this. I hope they applied that surface treatment? Its survived since March 2015 through some tough asks of boost and some knock events. So it must of been OK?


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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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