TwinSpark MegaSquirt conversion - Page 7 - Alfa Romeo Bulletin Board & Forums

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post #91 of 99 (permalink) Old 07-20-2015, 01:02 AM
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Originally Posted by aikendrum105 View Post
Thanks !

the Spica piece is hollow inside - maybe 20mls, it's more likely the 1.5m vacuum line to the ECU in the car that's forming a plenum to dampen the pulses.

Looking at the composite logger - MAP seems pretty clean...

The ITB tuning mode in the MS3 I'm using takes a bit to get your head around - but a few learned mates are pointing me in the right direction

A good friend is running the AH ignition and loves it. I didn't realise they were motorcraft coils - they are highly recommended by the tuners in the states I hear.

I was using the Motorcraft EDIS wasted spark coils (without the EDIS) without any probs, switched to a pair of the more compact DIYAutoTune 4 towers for a neater install, then moved them from the intake to exhaust side to tidy it up for the airbox, but I'm going to fit some COP units from the same GSXR I sourced the ITBs from to really tidy things up. (and because I'm silly that way) Will still run them wasted spark in serial pairs off the same Bosch 211.

The pencil coils are Denso 129700-4150/4400, about 3.5 inches from the top of the plug ceramic to the bottom of the electrical connector on the top. Shortest / smallest diameter plugs I've found so far.

Amazed at how many tuning options the MS3 + MS3X expansion board gives you.... fantastic stuff for so few pennies.
Hi Scott!
What kind of fuel injectors and at what pressure are you running?
It seems that TS stock injectors (0-280-150-702, 18 LBS/HR, ~190 CC/min) are really undersized for the factory claimed power output @ 3bar of pressure. My engine rebuild (head ported, but otherwise close to stock 155 type engine) is close to finished and I have a set of bosch type 3 injectors (21.35 LBS/HR) laying around. They seem to be a better fit to achieve the claimed hp and maybe a little more on the stock motronic.

My Alfas: 2011 159SW 2.0jtdm, 89' 75 2.0TS, 2x85' 90 2.0IE and 2.0v6, 83' Alfasud Berlina (1.7 8v boxer). Ex: 93' 164 (3.0 V6 12V), 96' 145 QV (2.0 TS 16V)
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post #92 of 99 (permalink) Old 07-20-2015, 03:45 AM Thread Starter
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Hi ! you've reminded me this thread is well due an update

I know what you mean re the injectors - I'm still runing the stock injectors and pressure - from memory I thought the standard injectors were good up to ~ 190hp at the upper end of their pressure rating... (memory is getting hazy there) so I was only going to upgrade them if the megasquirt was having to run excessive duty cycle at high rpm and load to keep the AFR right.

I haven't had an issue with them so far, but the current engine tune is only ~ 175hp. Engine is coming out for new pistons, camshafts and a couple of other mods shortly which should get me up around the 190hp mark. If you run a wideband O2 sensor you can keep an eye on AFR at high rpm and load - that might tell you if you need to up the injectors or not

I think the only risk of running the larger injectors is if they might make idle control a little trickier - the bigger the injector the less granular they can be at idle. I don't think a jump from 18 to 21 lbs/hr is going to be a massive issue though. The motronic is batch fire injection which contributes to that a little as well.

Are you going to run the stock motronic intake plenum and runners ? if you've ported the head and maybe opened up the valve seats a little - the next restriction can sometimes be the ID of the intake runners - they get pretty narrow in places

When do you think you'll be firing it up ?

Cheers

Scott

Scott Murray
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post #93 of 99 (permalink) Old 07-20-2015, 04:51 AM
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Hi Scott!
The engine is still in peaces - plan is to finish it until end of August. I have a trackday scheduled in early september, so I'd like to finish it until then.

Head porting is finished, modified valve guides going in and hopefully also valve seat will be reground this week.
I'm still waiting on crank balancer, but as I haven't received rings yet, bottom end can't be assembled yet anyways.

The intake runners have also been enlarged and matched to the head (as you know, ports actually don't line up from factory)
This is the intake runner and most of the material removed.


Matched ports to intake:




The intake manifold itself will also need some attention - the plan currently is to cut and weld the aluminum intake from 155ts engine I have (FWD intake can't be used in a 75 without modifications as it is well above hood line and 164ts has plastic intake - so it can't be easily modified).

To see if motronic can handle the increased flow and bigger injectors, I've bought a wideband controller (SLC free from 14point7), which I plan to use with a logger of some kind, but as I don't have any experience with ECU tuning I'm trying to learn as much as I can at the moment.

My Alfas: 2011 159SW 2.0jtdm, 89' 75 2.0TS, 2x85' 90 2.0IE and 2.0v6, 83' Alfasud Berlina (1.7 8v boxer). Ex: 93' 164 (3.0 V6 12V), 96' 145 QV (2.0 TS 16V)

Last edited by j.k.QV; 07-20-2015 at 05:37 AM.
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post #94 of 99 (permalink) Old 07-20-2015, 06:01 AM
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Btw. the motronic I'm going to use (m1.7 from 164ts super, series 2) has 2 separate injector channels, so I'm not entirely sure if it works the same way as 75TS, which has a common + and - for injectors, so only one injector channel.

My Alfas: 2011 159SW 2.0jtdm, 89' 75 2.0TS, 2x85' 90 2.0IE and 2.0v6, 83' Alfasud Berlina (1.7 8v boxer). Ex: 93' 164 (3.0 V6 12V), 96' 145 QV (2.0 TS 16V)
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post #95 of 99 (permalink) Old 01-16-2016, 10:16 AM
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Scott:

A few pages back you posted your initial spark advance table whereby all values were the same of each load value. Only rpm based. Have you modified that table? If so, can you post it, please?

Thanks for posting your work and findings,

Stefano
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post #96 of 99 (permalink) Old 10-24-2016, 01:16 PM
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After just rereading the thread the x-time i've been wondering whether the 38mm throttle bodies may (have) hindered power beyond the figure you had. Could that be?
Does anyone here know how ITB sizes relate to carb throttle sizes? From reading online 38mm (in your case) would be close or equal to a carb with a 38 venturi which wouldn't be smaller than a 45 carb with larger venturis which some guys here run with 150 hp+.
Quite frankly I'm wondering how the vacuum in the carbs for sucking fuel does hinder airflow vs ITB.

Learning, learning..
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post #97 of 99 (permalink) Old 10-26-2016, 05:47 AM Thread Starter
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Hi Allessandro, another great question ! The throttle bodies are straight through (well - there is a slight taper which is 38mm at the smallest) a set of 45 dcoe's with a 38mm choke will have more restriction due to the secondary venturi's hanging in the middle of the port - so the 38mm ITBs will flow better of course.

Because the ITBs and Injectors aren't dependent on air speed giving venturi effect to draw fuel - you have less problems with low speed air stall with larger bores than you would if you ran a set of weber 45's with 38 or larger chokes.

The other thing to remember even with an excellent Jim K style porting job on the intake ports, you are still faced with intake ports 38mm dia or lower (with a valve stem and guide in the middle of it) so going to a bigger throttle body doesn't help with flow.

What a bigger ITB (or 45 dcoe) gives you is a bigger butterfly valve - which can offer a snappier throttle response (or very sensitive throttle - depending on your definition)

This is a bit of a running argument I have with friends around which throttle body diameter to choose - some have insisted on going to 45mm ITBS (because Weber 45's right ?) and end up having to 'gear down' their throttle linkages to deal with the sensitive throttles - and also with air stall / bog down issues at lower RPM.

Just a couple of my thoughts anyway - more learned denizens of the forum may be able to shed a little more light on it

It's great fun working it all out though, isn't it !

Cheers,

Scott Murray
'04 156 JTS Sportwagon -- brilliant car for the daily, kids taxi and parts hauling

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'65 Giulia Sprint GT 105.04.753710

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che figata -

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post #98 of 99 (permalink) Old 11-29-2016, 11:41 AM
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High Performance Math

Would say 42-45mm depending on where you want your peak tourque to be.
I can agree with the math here for TB as I have checked MANY different calculations online, and for ITB's I will be going with around 42mm, just because I want more airflow lower down in the range, and don't mind giving up a smidgen up-top.

Enjoy the calculator's they are fun.
Ian
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post #99 of 99 (permalink) Old 11-29-2016, 06:30 PM Thread Starter
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That's a great resource all on one site - thanks !

I think once you go bigger than the effective 'diameter' of your porting, seats, valves and lift area - you're adding snappier throttle with the larger butterflies (and maybe risk of air stall), but the head is still the limiting factor I guess.

If they're tapered though they might become effective intake horns which can be handy in a tight space

I love this stuff

Scott Murray
'04 156 JTS Sportwagon -- brilliant car for the daily, kids taxi and parts hauling

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'66 Giulia Super 105.28.720988 -- TwinSpark+MS3+ITB+COP
'65 Giulia Sprint GT 105.04.753710

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