refresh951

haha. I get 4-5 hrs a day whether I need it or not.

1/4 NPT weld bung with brass nipple fitting.

The nice looking welds were done by a friend of mine, the bad looking one were done by me. I think aluminum tig welding is like playing a guitar, i requires quite a bit of practice.

One of my business clients has a really nice Miller AC/DC Tig they said I can use any time so I used it. I Almost bought an Eastwood Tig but really could not justify it. I do have a Hobart MIG and I tried to tack this stuff but had trouble with the wire feed. The spool gun would be a must I believe.

Thanks Sid. Was going to to call you this weekend and hopefully pick your brain on a couple things before I hit the dyno.

blown 944

I'll be around

CyCloNe!

looks great Shawn! Pipes look beefy, probably could fit a few gerbils in there

refresh951

Finished putting everything back together last night and made some test runs today and the changes feel really good. Running the motor retarded by 3 degrees. With some minor timing adjustments I cannot feel any difference on the bottom end. Tomorrow I will get some logs on the freeway so I can open it up more and try to get a feel for the top end. I think this approach is going to work.

The new 160# 5th injector seems to be working great. Idle was perfect. Interesting that sitting at idle, a good bit of condensation was forming on the IC pipe just past the injector carrier. Humidity was at 89% so the IC pipe was definitely at a temperature below ambient. I think testing will show I am getting a good bit of intake temperature benefit from the 5th injector.

I was getting a rattle from the new exhaust and had to adjust the mounting tab at the muffler. No rattle what so ever now. I am really happy with how it sounds and looks.

Also, today I messed with the balance shaft phasing and got it dialed in perfectly. I had a bit of vibration that has bothered me. Nothing terrible but just enough to be annoying. I had this with the 2.85L also. I could see it at idle by watching my Diverter Valve vibrate. Pretty understandable considering the changes in stroke and lightning of the internals. Through some trial and error, I moved the lower BS one tooth clockwise and the top BS one tooth counter-clockwise and it was noticeable improvement. The DV vibration disappeared completely.

333pg333

Really does look fantastic Shawn! You're to be congratulated.

With regards to the changes made to the hardpipes and also in context with what we were talking about, would you say that running a larger diameter hardpipe than the throttle body could prove problematic? What size is your T/B anyway?
Also, what size downpipe and exhaust are you running?

refresh951

No doubt the TB is too small at this point. I am looking at options: I have a 928 TB, the Audi TB, and big bore TB mod. I did make some modifications to the stock TB to improve it a bit but it will have to be addressed. Downpipe and exhaust are 3" with a WG dump.

333pg333

Do you think that having larger pipes coming into a smaller by comparison T/B would create a bottleneck/friction/stall situation?

Dougs951S

Shawn, shame on me if this has already been discussed but I'm thinking very seriously about starting a hybrid stroker build of my own. I have access to a good block, crank, and cam sitting around. Just needs a head. What -cc where your dished pistons? I did some rudimentary calculations and I may have made some errors and incorrect assumptions, but with a 102.36 x 86 motor, a compressed HG thickness of .97mm, 56cc combustion chamber volume, .01 deck clearance, and -31CC dished pistons I calculated my CR to be ~8.4:1. This is about where I would like it to be, but arn't you running less compression than that on the 3.1? If so, how did you manage to drop the compression down, I could not find an off the shelf piston with greater than a -33cc dish? I ask more out of curiosity and to get some tips for a 2.85. Thanks!

refresh951

The new IC pipes have a 2.37" ID and the TB plate has a 2.20" ID so it is not a huge difference. I think it is a restriction but I do not think it poses any operational issue. On the original IC pipes the hose off the turbo necked down to a 1.62" ID

I used these pistons on the 2.85L (-31cc inverted dome):

http://www.jepistons.com/Products/148750.aspx

I used these pistons on the 3.12L (-16cc inverted dome):

http://www.jepistons.com/Products/138103.aspx

My 2.85 L was not a non-interference design.

Are you using a engine calculator something like this? Are you using a 2.5 L crank? Remember you can adjust the CR by taking a bit off the stroke. Also, look at different pin heights.

http://www.eaglerod.com/

Dougs951S

Shawn, the first pistons you linked are the exact pistons I was looking at. My thoughts were that they could be flycut slightly to allow a non interference fit. How much deck clearance is required of course depends on the pistons chosen, but it seems like I dont have too many options to play around with different pin heights if I want to have a decent CR. Using a 2.5 crank and block. I definitely cheated, and have been playing with some applications online. Those pistons give me 8:1 with .033 clearance. If I take the stroke down to 84 mm that would yield 8.3:1 and .072 clearance if I went with a -16cc piston and 1.425 pin height. I would also lose 65cc displacement compared to yours and sid's 2.85 build.

blown 944

Don't stress about the deck clearance. I can assure you that as long as its within reason you'll be happy. Cutting a little off the stroke is fine too.

It doesn't require much fly cutting either, so either way (shorter stroke for more deck clearance or fly cut) you slice it you'll be happy. I have built both and both work well.

Dougs951S

Did you guys end up using the 5.9 or 5.906 rods? I suppose it wouldn't matter all that much, I know the stock 951 rods are 5.906. What would you guys consider an ideal compression ratio for an engine still running motronic? I'm thinking about building a 2.80L engine with a slightly shorter 85mm stroke and ~8.8:1 CR because nobody has built a high(er) compression hybrid stroker yet.

refresh951

5.9 Eagle Mitsu rods. What are your power goals?

Dougs951S

My goals are a reliable, solid 400 rwhp with close to stock turbo response and much improved off boost performance. The turbo I have is more than capable, but I'd like a bit more low end grunt and the peace of mind from having a stronger, lighter rotating assembly. The other benefit I see is more efficient highway cruising because of the increased compression. This motor will be E85 fed.

blown 944

The 2.85 would easily hit what you want. However, the long stroke engine has proven to add quite a bit of extra torque off boost. Considering is a small difference in price in the grand scheme, I'd just start with it.

Btw, you can get decent mileage by fine tuning a "lean burn" cruise situation.