Megasquirt ignition map for TC turbo

Road-race engines and ancillaries - general discussion
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pacman
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Megasquirt ignition map for TC turbo

Post by pacman » Sun Aug 14, 2011 6:36 pm

All,

The past winter I built a new engine for my seven clone. It is based on a 2 liter block from a US Fiat 132. The reason for choosing this block is because it a low-smog engine with a CR of 8.0:1, well suitable for turbo charging. Flat top pistons. For this motor I used basically all other components from the previous 1756 with some minor modifications.
The head is a 124 sport coupe 1756 with casting no 4301155 (132 AB1AO) which i've been told is a good head. I don't really know what the actual CR is with this head compared to the original on this 2 liter block, but a wild guess is that it shouldn't differ too much from 8:1.

I have only made a few shorter runs during the summer due to cooling issues which i hope i have finally solved. (Air pocket in the radiator...)
So when i now have a more reliable cooling I've finally started with fine tuning the fuel and ignition maps.

Attached is the ignition map i'm currently using. Fuel is 95 unleaded, CR 8:1 with original 124 1800 sport coupe cams. I need your opinions. Is it too aggressive at part load and boost?

Regards
Peter
Attachments
Ignition map 20110814.JPG
Ignition map Fiat TC 2liter turbo, CR 8:1
Ignition map 20110814.JPG (85.31 KiB) Viewed 2820 times
Seven-clone builder

WhizzMan
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Location: Amsterdam, the Netherlands

Re: Megasquirt ignition map for TC turbo

Post by WhizzMan » Mon Aug 15, 2011 9:02 am

To me, for a compression ratio of just 8:1, it doesn't appear overly aggressive on first glance. However, it's not possible to give any accurate judgement without "det cans" and a rolling road. You really need to have a way to detect detonation, and measure at which advance you get optimal torque to tell what is good. My advice would be to go easy on anything over 30 or maybe 35 degrees for safety (temporarily) and get over to a reputable dyno to get it mapped properly. It may be a step back, but if it was mine, I wouldn't want to break my new engine on a gamble, or a guy on a forum saying it's safe.

Keep in mind that once you start forcing induction, these maps should be retarded on boost.
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pacman
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Re: Megasquirt ignition map for TC turbo

Post by pacman » Mon Aug 15, 2011 9:50 am

Keep in mind that once you start forcing induction, these maps should be retarded on boost.
Everything over 100 Kpa is on boost, hence the lower values.

/ Peter
Seven-clone builder

timinator
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Re: Megasquirt ignition map for TC turbo

Post by timinator » Tue Aug 16, 2011 4:07 am

Hi Peter, Not a lot of information to go on. I assume you don't have any experience with turbos, so your learning curve will be expensive.

I would guess that you can't make anywhere near 250kpa so reconfigure your map to 175kpa. That will give you more matrix points that are in your usable power range. Most of your map are places that normal driving will not enter.

The na cam will build boost very late and somewhat slowly. The part of your Megasquirt map of interest will be from 4000 to 5500rpm. Assuming that you have installed injectors about three times stock capacity (and have installed a fuel pump that will keep up) this region is where bad things happen so fast that you need every data gathering device that will fit in the car to understand what is going on.

The ignition timing under boost in this region of 4-5.5k rpm is more than you can use, back it down by at least 5deg. I would guess that about 175kpa and 5500rpm will be your boost spike so set the timing there about 16deg. From there your boost will decline (unless your have boost control you didn't mention) so timing becomes less critical. It is always best to be conservative with all your tuning until you know what is going on.

You didn't ask about fuel, but here is my suggestion. Turbos at full load run fine at 11:1 afr, going lean means 12.5:1afr, so stay rich until you are dialed in. Also, 100kpa isn't where your boost starts when you are at 4000rpm with your foot to the floor. A na engine would be at 35kpa at 4000rpm and full throttle.Good luck.

Tim

pacman
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Re: Megasquirt ignition map for TC turbo

Post by pacman » Tue Aug 16, 2011 8:39 am

Tim, do you have any experience with turbocharged engines? I do have some...

175kpa max? Factory setting of the wastegate is 0.85 bar on my TD04-15T unit (SAAB 9-5 Aero). MS boost control is used to adjust boost level above that with a fast acting valve.
Injectors are big enough...

We have always used the common retard of 1 - 1.5 degree / 0.1 bar boost and it have worked just fine so far
My concern is really the off-boost advance levels. Since we on previous engines have had CR of 8.9:1 and higher i'm curious if we could use more advance due to current CR of 8:1.

AFR at high boost is set to 11.8:1 which is a normal level for most engines. AFR at cruise is 15:1. 11:1 is too low and a waste of fuel.

35 kpa @ 4000 and WOT???

Peter
Seven-clone builder

timinator
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Re: Megasquirt ignition map for TC turbo

Post by timinator » Tue Aug 16, 2011 5:02 pm

Hi Peter, Seems I annoyed you. Sorry.

Kpa isn't my unit of choice. Most stock turbos run 5 to 15psi. I was making that assumption. Evo and wrx can go to 19psi. I run my Evo 8 9.8 to 23.5psi where it starts to overheat the intake charge.

Standard retard based on boost got me into trouble when I first started because I didn't know all the other things that were affecting my engine. As GC points out one must spend way to much time going cell by cell to correct timing and fuel.

I didn't say anything about running at cruise with 11:1afr. At full boost it is no problem as opposed to being lean, which can kill a piston in a heart beat. I always suggest that one be conservative when tuning and that means rich with a turbo.

Your concern for off boost advance puzzles me. The difference between timing an 8:1 and 8.9:1cr engine isn't worth discussing.

I am curious why you didn't cc the head you are running while it was off. I have found as much as a 2cc difference from one chamber to the next on the same head, let alone not even knowing what it cc's.

Next time you are driving your car at cruise at 4000rpm smash the throttle to the floor and tell me what your manifold pressure is. I realize 35 kpa was incorrect. What I meant to say was 5 inches of vacuum.

I have run na cams in a turbo engine and it wasn't bad. It just wasn't good.

I assumed a lot because you posted so little. I hope we can continue to discuss your project.

Tim

pastaroni34
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Re: Megasquirt ignition map for TC turbo

Post by pastaroni34 » Wed Nov 09, 2011 7:18 pm

Peter,
First of all, glad to see you're using MegaJolt! :) Second, your map looks pretty good, I have a few suggestions:

1. Your off boost advance @ 40deg is a bit high, I wouldn't go over 37. Granted, you probably never make it to these load cells.

2. You will benefit from rebalancing your load and rpm bins. For instance, between the 3500 and 7000 columns, your advance is very nearly linear. There's no reason to have the extra bins in between. You could have more bin resolution near the rpm when you come on boost, which is the most critical region of the map.

3. Its not directly related to mapping but if you don't already have IAT correction, you should add it as an additional input. It is really helpful, at least here in Texas where ambient temperatures are over 105 deg.
-Jason Miller
Miller's Mule Machine and Design Inc.
Houston, Texas - USA

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