Alfa Romeo Forums banner

1 - 20 of 32 Posts

·
Registered
Joined
·
2,169 Posts
Discussion Starter #1
After much trial and error I managed to get my Megasquirt Spider project running for the first time today. Since nearly everything I've seen on Megasquirt for Alfas is tailored to either the V6 or Twinspark crowd I've tried to document what I've learned for posterity including specific part numbers for everything I had to source to make it happen. This build was based on a Bosch vintage Alfa engine including intake manifold and plenum.

The file is a 3.7MB PDF with plenty of pictures. I'll add more detail as I get further into tuning, etc. but since the car is now running I think I can call the basic approach a success.
 

Attachments

·
Premium Member
Joined
·
14,298 Posts
Congratulations on finishing the install and thanks for the excellent documentation. There are many days when I wish that my Spider has Megasquirt.
 

·
Registered
Joined
·
2,169 Posts
Discussion Starter #3
Thanks Ed. I was a bit surprised that there wasn't more info out there on doing Megasquirt on Alfa engines. I guess my thinking was that having an easily repeatable pattern for cheap EFI on a Nord it would give another option besides spending $1k or more on a Weber swap or a rebuilt SPICA. The superior performance, economy, and emissions of programmable EFI is of course a big bonus.
 

·
Registered
Joined
·
4,199 Posts
I wish you hadn't done this. I'd obsessed over a Megasquirt several years ago until I finally convinced myself that I like the original tactile responses of a Weber equipped Alfa. While I still like the way a Weber equipped Alfa sounds and drives, you've got me thinking about installing a Megasuirt again . . . dammit. :)
 
  • Like
Reactions: horsewidower

·
Premium Member
Joined
·
14,298 Posts
I have a hot 2L motor with 45 Webers and a hot 3L motor with Megasquirt and I tune both of them. It is not difficult to get the Webers good at WOT, high RPM but the midrange just lands where it is. You have some control with emulsion tubes and alternative main jet/Air corrector combinations but it will never be better than a good compromise. There are 100 bins in the Megasquirt fuel table that are either filled individually based on AFR observation, etc or adjusted automatically when you turn on the auto-tune.

My 3L motor is set up to produce an AFR of 13.2 +/- 0.2 all the way from 3500 to 7000 rpm but I was getting lousy gas mileage - about 14 mpg average. Just recently I set up the AFR table with 13.2 at all high VE, 14.7 in much of the remainder and 15.5 in the cruising condition - 50% - 70% VE and 2500 to 4000 rpm. Now the mpg appears to be in the mid 20's - better than my Spider in a heavier car with about 60 more HP.

My next project is to install a PWM idle air valve to replace the sorry L-Jet device.
 
  • Like
Reactions: horsewidower

·
Registered
Joined
·
116 Posts
Great write-up! It is very generous of you to go to all the trouble of documenting everything so others can benefit. You should post a link to this thread in the Spider section.

I would love to follow your lead and it is great that you did fuel and spark. However, it is a little outside my comfort zone, so it will have to stay on the wish list.
 

·
Registered
Joined
·
4,199 Posts
Slowly, slowly, I turn, resisting the impluse until . . . . You know what would be really cool? We could get a pair of the Jenvy throttle bodies that are made to look just like DCOE Webers, except they're not, they're really fuel injection throttle bodies. Then we could use an oem Weber manifold and carb linkage along with stock airbox and a plenum. We could have a Megasquirt ECU managed engine that retained it's classic Portello era 105 Alfa underhood appearance! Ugh, I think I need a aspirin.
 

·
Premium Member
Joined
·
2,874 Posts
I'm still fiddling with adapting the SPICA ITBs to electronic FI. I like a stealth look.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
2,169 Posts
Discussion Starter #10
I thought about the Jenvey TBs. Ultimately decided that when there's a perfectly viable factory intake manifold and plenum available for peanuts it's kind of hard to justify the cost of the TBs. And of course then you'd need to come up with a custom throttle linkage and fuel rail.
 

·
Registered
Joined
·
4,199 Posts
Actually you don't the Jenvey throttle bodies, regular and DCOE style, use standard Alfa Weber linkage. Although they look cool, they are pretty expensive, however.
 

·
Premium Member
Joined
·
14,298 Posts
Jason's set up is simpler than ITB's because he can get a good MAP signal from the plenum. With ITB's you will need to get a composite signal from the four or use throttle position instead of MAP.
 

·
Registered
Joined
·
2,169 Posts
Discussion Starter #13
Jason's set up is simpler than ITB's because he can get a good MAP signal from the plenum. With ITB's you will need to get a composite signal from the four or use throttle position instead of MAP.
Can you use just a TPS for Megasquirt? I thought the recommendation was TPS plus MAP, MAF, or both.
 

·
Premium Member
Joined
·
14,298 Posts
Can you use just a TPS for Megasquirt?
I am pretty sure that Al Mitchell has implemented one. It is like electronic SPICA with much more user control.
 

·
Premium Member
Joined
·
1,935 Posts
Well done, Jason, and thanks for the write-up!
 

·
Registered
Joined
·
1,271 Posts
Excellent thread and documentation. Thank you. Can you provide some details regarding your engine modifications? Or, did I miss them?
 

·
Registered
Joined
·
2,169 Posts
Discussion Starter #17
Excellent thread and documentation. Thank you. Can you provide some details regarding your engine modifications? Or, did I miss them?
The engine has a Richard Jemison ported head with RJR 550 / 785 cams, Motronic pistons modified per Richard's direction, ceramic coated headers, and a Magnaflow exhaust. It should get up and move pretty well once the FI is all dialed in.
 

·
Registered
Joined
·
16 Posts
I am looking to wake up my 1988 Spider engine and found your document very helpful. I am no expert at all, just trying to piece it all together. I am wondering if the larger injectors will get enough air at mid range and WOT with the L Jet throttle body and plumbing to the intake plenum. You might not be able to really tell if this is the case until the engine is under load. What are your thoughts on this point? Thank you.
 
1 - 20 of 32 Posts
Top