Setting timing for bolt on turbo to N/A engine.

[grillhands]

Hello. I have a N42 block with a P79 head which apparently lowers my compression to 7.8:1 according to http://datsunzgarage.com/heads/ . Through my research I've found many people who did this conversion tend to lock the vacuum advance and set timing to 22-26 degrees advanced. I've also seen one or two people set theirs at 15-17. They all pretty much have stock turbos and front mounts. My question is where are they coming up with these numbers? I've just read a topic on here about detonation where Tony D and Gollum I believe but up some interesting information. With that being said I want to avoid detonation as much as possible. Currently I'm using the stock n/a efi with fmu, wideband and front mount. Megasquirt will eventually be had once I get more comfortable with the installation and tuning process.

 

Thanks,

 

Matt

[Kennymonster]

I'm not too familiar with stock EFI system's limitations and what you can add on, but I was using MSD 6A with a boost referenced retard module on my NA turbo set up (it was a carb'd blow through). http://www.summitracing.com/parts/msd-8762

 

Locking the timing at a fixed amount is probably not the greatest route, might be ok on idle / WOT, but I can't imagine how sluggish 7:8:1 motor would run at partial load / cruise with 20 degrees timing. The retarded timing would increase exhaust temps as well I think.

 

With the MSD boost retard unit, using a zx distributor with 17 degrees centrifugal advance;

 

- I had my idle set at 17 btc

- At 3000 rpm (off boost) 34 degrees all in (didn't use vac advance but probably could)

- Starting at 2 psi (can set 1 to 5 psi when the timing retard kicks in), I had my MSD dial retard 1.5 degrees per psi (maximum of 15)

- So running 10 psi with a FMIC on my 8:7:1 motor, (10 psi x 1.5 = 15 degrees retard from 34), it was at ~19 degrees on WOT @ 10 psi

 

On your motor you could probably afford to do low mid 20's and still be ok, and have around 20 degree BTC which will help start up and off boost response. I'm probably going to sell the MSD unit since I'm reverting back to NA, let me know if you're interested or need more info on the set up and I'd be happy to oblige.

Edited January 28, 2015 by Kennymonster

[grillhands]

Thank you for the response. My 280z is an absolute dog. I can't keep up with a Geo Metro if I tried! How did your car drive with that setup? Did you have any issues with detonation?Also, did you leave your vacuum advance hooked up or did you plug the ports?

Edited January 28, 2015 by grillhands

[Kennymonster]

When the motor was at its peak, at 19 - 20 degrees under full load @ 10 psi, it seemed to run strong without detonating. I have a higher comp motor but also had a mild cam as well. 

 

It was very sensitive to anything more though, ~22 - 25 would ping right away with the full boost / under load. Keep in mind that I had a higher comp NA motor compared to your set up however.

 

Depending on the lb's of boost you're running, you should be able to dial it in something close to 20 base, 37 off boost, and 22 or so @ 10 psi, or slightly more if you're boosting less than 10 psi.

[grillhands]

This may be a dumb question but all the numbers are for before TDC, correct? How much are you asking for your msd setup?

[NewZed]

Relative to what you need to know to get your engine running right, yes, the question above is "dumb".  You need to learn the basics of how a typical engine works.  Your lucky yours hasn't self-destructed yet, if it's not already damaged.  You mentioned stuff that's bolted on but haven't even said what your timing is set to, initial, plus vacuum and centrifugal advance totals.  You'll need to understand it anyway if you get the MSD unit. Many of us have damaged many parts, from your current knowledge level.  Better to read a lot more and get a cheaper education.  

 

It might seem backward but the more primitive your engine management system is the more you need to know to get it to work right.  The only "improvement" to your stock system is the FMU and all it does is add more fuel than stock based on manifold pressure (aka "vacuum), depending on how it's set up.  You're in the Stone Age.

[Kennymonster]

^Basically this. The point is ignition timing is absolutely crucial and can mean the difference between a well running motor, or pre detonating to death in just seconds. All in a matter of few degrees.

 

The boost timing unit was purchased 260 new and MSD 6A was 199 new, however I'd let both go (you need both to work), for 190 + ship. I'd advise seeking fellow z tuners in the area for assistance though, as hands on advice might make more sense than online information for your set up.

[grillhands]

The car has never been started. Im in the process of finishing the conversion. I've built plenty of high horse power vw engines put I left the tuning for someone else. I have no confidence in my ability to tune lol.

Edited January 29, 2015 by grillhands

[Kennymonster]

Everyone has to start somewhere, I would do a lot of reading on rising fuel pressure regulator + ignition timing map for L28 turbo set ups. It's always good to have some knowledge on at least the basics, even if you don't do the tuning yourself.

[frodriguezvsi]

Does anyone know if MSD-6btm will trigger a Megasquirt from the tach output to tach input of megasquirt?

[NewZed]

The guy who knows already said yes.  We all can see all of the threads, no need to keep asking the same question everywhere.

[frodriguezvsi]

so how do you wire up an MSD to Megasquirt?

[Kennymonster]

MSD is actually great with PDF wiring diagrams and active tech support, if you can't find the wiring on their site, try their forum for a quick response. Their reps are constantly on there answering tech questions.