madkaw

Vacuum Advance- how is it supposed to work? - ChevyTalk --The Social Network for Chevy Fans

Hope Guy doesn't mind this thread diversion. VA is to help with emissions and MPG . It should only be involved during low load high vacuum situations. That's why I asked if this is a racing motor. Running a street dizzy on a race motor is a compromise anyhow, but having the VA working will probably limit total timing under full load( using OEM figures)- which you don't want .

Jeff, Not sure if I've ever seen timing checked WITH VA attached. The 55 you are seeing is probably with 17 degrees vacuum advance. I think that dizzy adds 17 degrees mechanical. Is this a race motor? If so , I would forget that VA and run around 17 initial. How much mechanical advance does the spreadsheet show?

Timing is probably critical with that turbo charged engine. OEM timing might not be relevant and the OP might find that initial timing is way advanced and mechanical timing has been deactivated . Pressurizing this motor changes many parameters of tune on this motor. The BIGGEST change will involve timing. Stock timing could be the demise of this motor. I would be not be surprised to see timing at 18-20 degrees PERIOD

So all the plugs looked the same? If they did, then it's something that effects all of them at the same time like ignition being weak, too much fuel pressure , etc.

I guess I don't need to mention that engine temp is critical with engine tuning. You might get that resolved before continuing the tune Good luck

And as far as the "flat top" carb, it might be the best SU for this application . The flat tops have a separate idle circuit which would be ideal for this turbo set up- which might also be the reason it doesn't idle now. With a separate idle circuit, you can have the main circuit run rich for pressurization .

How about some closer pics of the carb and the hoses going into it. Are you sure you got the hoses in the correct places? I'm curious about the hose coming off the top of the carb to the valve cover. Seems like full vacuum from the intake on the valve cover?

Remember , using a stock dizzy like I am limits me. To reach my total advance numbers I am forced to increase my initial advance, but I have no issues what so ever running 18 + degrees initial. You have much more flexibility and with proper tuning should be able to extract more HP from your motor just with timing. That's why I am installing MS and doing away with my dizzy all together

I don't think you will find much info on hear concerning graphed timing curves. As posted above, using someone else's curve might not work for your engine anyway. There are very few L26 s with a MN47 head around here -let alone with your cam. My only suggestion would be to make a good hearing device to pick up the sound of detonation. You can search for what others have done on the internet as far as putting a mic somewhere on the engine and wearing a headset of some kind to listen for pinging! They say the human ear is the best anti-knock sensor. You can try all types of springs, but unless you have an accurate butt-dyno, it will be hard to tell your results. You could try the knock limiting approach and max out timing to just before pinging, but is that where best MBT is? Only a dyno would tell. I would think the MN47 would be a very efficient head and you might not need to much timing to reach MBT. I have a small chamber head with my early e-88, and I run a lot of initial-18 degrees with no VA. I max out with 35(17 degrees mechanical) When I dynoed my car I started out with 37-38 total timing. I backed of the timing to 35 and saw no difference in MBT. I would think with triples you would want more initial then 10-IMHO

I am doing a Megasquirt conversion now. You need to get on the Megasquirt site and read, read, study and read some more. This is not the best site for your goals. You would be better off on Hybridz where this work has been done by many. There are many members who have posted their projects in great detail and will be helpful to you. The megamanual is probably one of the best resources also

You wouldn't be the first to leave the ratchet on that bolt!! Congrats on getting to drive all that hard work- it's a great feeling isn't it?

Can you elaborate more about what's blocked off and do you have anymore pictures showing the induction system ?

Timing light?

The other thing that would have jumped out at me was the rain storm. I would have suspected moisture under the dizzy cap would have caused the misfires .

When I said dirty tank, I picture you stirring up crap during fill up and this crap initially getting sucked into the sending unit. After sitting for a period of time the crap falls out and things are good again. Have you peeked inside your tank.

Haven't watched the video but the first thing that pops in my mind is dirty fuel tank

Hmmm, that is weird

Not a lot of help to find here on the L28 turbos. Someone just put a lot of work into an engine timeline which was nice since it laid out the different year heads and blocks. The easiest way is to find a complete 28ET motor because you will have all the parts( exhaust , oil pan, plumbing ), or just find the best deals on stuff and throw any motor together and pressurize it, just keep the CR down a bit. As far as LSD, do the STI swap and don't look back. OEM Subaru quality with choice of ratios and made in this century and plenty good for most moderate HP goals .

Chris, You kind of threw us a curve ball. You never mentioned that you removed the oil pump during engine swaps- which I wouldn't have assumed since its not necessary. Since you said the motor ran great before hand we were all thinking of things you might have touched, but I didn't figure on the oil pump. Anyway, it made for interesting reading

How do you know you are close on timing? You can't check static at 1800rpm, so what advance to you show at your present idle? Sounds like your effort needs to be somewhere other then carbs at this point. There was just a 7 page thread with similar issues and it turned out to be timing. The fact that you know little about this engine, someone could have clocked the dizzy drive wrong.

Not a real definitive source of the issue, but it sure sounds like timing way advanced maybe? There's another thread going on that has haunting similarities. Glad you get to move on!!

Have you tried to alter timing-retard it? Does it fire up easy everytime? It seems that the timing might be way advanced. Linkage-what have you done to eliminate that possibility? What's the history on the engine? Have you ever heard it run right, or did you buy this and started out this way? What year car and engine? What distributor are you running? I have no answers, just questions:)

Sounds like Blue is a true "petrol head"! Also sounds like something I would do. I travel myself and sit in a hotel half the week and wish someone wanted some wrench help near by to get me out of the hotel. It doesn't suprise me that Phillip would do this as much as he takes time to offer his insightful posts on here. The pictures and detail of his write ups shows what a Motörhead and enthusiast he is. Good story and thanks for sharing

Any aftermarket shifter made for the T-5 trans should work. I guess I don't understand the "scarce" statement. The shifter is BW, not Nissan. So any shifter that will bolt up will work. As far as the boot, that's another story. I used the ZX boot because it's bigger, heavier, and seals nice. I believe I used the inner and outer both to keep things quiet. I'm using a Pro-Tower shifter with adjustable stops and it is sweet-90$ off of craigslist new in the box! I still have the original shifter in perfect condition if anyone needs one!