Home  |  Forums  |  914 Info  |  Blogs
 
914World.com - The fastest growing online 914 community!
 
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG. This site is not affiliated with Porsche in any way.
Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners.
 

Welcome Guest ( Log In | Register )

> Going to Megasquirt, More questions
bbrock
post Sep 11 2021, 10:46 AM
Post #1


914 Guru
*****

Group: Members
Posts: 5,269
Joined: 17-February 17
From: Montana
Member No.: 20,845
Region Association: Rocky Mountains



After about 1,700 miles of driving my freshly restored car with rebuilt engine, I’ve decided I’ve had my fun with Weber carbs and distributor-based ignition and am ready to step up to modern EFI and coil on plug ignition. Even with the jetting that came out of the box leaving the carbs running rich, the performance has been fantastic. What is not fantastic is the garage stinking of gasoline, no compensation for altitude, and being generally too fiddly to set up for my taste. My trials with the ignition are documented in another thread. Yes, I know a 1-2-3 would solve those problems but for the money, I’d rather invest in modern COP ignition as part of an EFI upgrade.

My goal is a smooth, efficient, and reliable street machine that I can drive from sea level to 11,000 ft. without starving or choking on fuel. Efficiency is at least as important as performance. As long as I can get at least the stockish 100 hp, I’ll be happy and beyond that, I’d like to wring as many mpg out as possible.

The engine is a mostly stock euro-spec 2L engine. The only mod is a fairly mild Elgin 6048 camshaft with 256 duration for the carbs. A source of pride of this build is this custom 911/914-6 inspired air cleaner I made which I think looks cool and really silences the carbs.

Attached Image Attached Image

Now for the questions:

• Single throttle body or ITB? I think I’ve made a decision but still interested in thoughts. I was thinking about welding injector bungs onto the carb manifolds and using my carbs as throttle bodies. The main appeal is that I would keep my cool air cleaner to make the other kids jealous. However, it seems the stock throttle body would greatly simplify the conversion. Also, even though the custom intake is designed to allow access for servicing and easy air filter replacement, it does crowd an already crowded engine bay and makes working in there just that much more of a challenge. My stock TB needs some TLC and might have to be sent for professional refurbishing. I think I could sell my carb setup to cover that cost but not sure. The upshot is that I’ve all but decided to go back to the stock TB, but curious what others think.

• N Alpha, Speed Density, or MAF? I’ve been reading up on this and think I understand pros and cons, but still a little confused about sensors needed. With my efficiency goal, I think MAF is the way to go. It looks to me that cutting off the tube connecting the stock air cleaner to the TB and replacing it with a MAF could be a really slick way to add MAF in stealth fashion. Has anyone done this? If not, how does one find the right MAF to use? Other than dimensions, what else needs to be considered?

Another question is about MAP + MAF vs MAF only. I’m a little confused about advantages or when a MAP sensor is needed if you have a MAF.

• Barometric correction – this is an important feature for my location, but the hardware needed to implement it is a little confusing. It seems like if you are running a MAP, then barometric correction is obtained by adding a second pressure sensor (another MAP?) to read reference atmospheric pressure to make corrections to the fuel mixture. How does it work with MAF? Do you only need one pressure sensor to read atmosphere? Or do you still need to reference it against manifold pressure? I assume a lot of this is done in the software but I haven’t looked to far into the tuning part yet. I’m more trying to figure out a shopping list for parts at this point.

• Anyone running a CAM sync and sequential spark and injection? Again with the efficiency goal, this is appealing. Looks like Mario is working on a new version which isn’t available yet, are there alternatives available? It seems people say you still need a crank position sensor even with a cam sensor in the mix. It isn’t entirely clear why though. Lastly, and this is mostly just curiosity, but is it correct to think that the lifespan (in miles) of spark plugs are cut in half with wasted spark?

I have many more questions but this is already too long so will save them for later.
TIA
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
 
Reply to this topicStart new topic
Replies
falcor75
post Sep 13 2021, 11:14 PM
Post #2


Senior Member
***

Group: Members
Posts: 1,579
Joined: 22-November 12
From: Sweden
Member No.: 15,176
Region Association: Scandinavia



I went the ITB route for my 2.3 but my car isnt built for daily driving or milage. Its more of a autocross and country road dasher. I got the camsync for mine and its installed and hooked up but we didnt end up using it. The reason is that the car drives fine without it in Alpha-N and wasted spark. My yearly milage between april and october is around 1k or less.

What I'm most happy with my set up is the noise and the crisp response and the bluetooth monitoring that allows me to display engine data in a tablet on the dash.

What I'm not happy about is the low idle at startup for the first minute untill the engine heats up a bit. With my ITB's I would need to add an idle air control valve to really sort that out.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
GregAmy
post Sep 14 2021, 06:00 AM
Post #3


Advanced Member
****

Group: Members
Posts: 2,390
Joined: 22-February 13
From: Middletown CT
Member No.: 15,565
Region Association: North East States



QUOTE(falcor75 @ Sep 14 2021, 01:14 AM) *
What I'm not happy about is the low idle at startup for the first minute untill the engine heats up a bit. With my ITB's I would need to add an idle air control valve to really sort that out.

I spent a lot of time managing startup, controlling the AFR with WUE and idle RPM with ignition timing control (Idle RPMs Advance Timing)...and mine starts foot-off, with no aux air valve, and pretty much cores it.

It can be done w/o an idle control valve.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
jd74914
post Sep 14 2021, 07:10 AM
Post #4


Its alive
****

Group: Members
Posts: 4,813
Joined: 16-February 04
From: CT
Member No.: 1,659
Region Association: North East States



QUOTE(GregAmy @ Sep 14 2021, 07:00 AM) *

QUOTE(falcor75 @ Sep 14 2021, 01:14 AM) *
What I'm not happy about is the low idle at startup for the first minute untill the engine heats up a bit. With my ITB's I would need to add an idle air control valve to really sort that out.

I spent a lot of time managing startup, controlling the AFR with WUE and idle RPM with ignition timing control (Idle RPMs Advance Timing)...and mine starts foot-off, with no aux air valve, and pretty much cores it.

It can be done w/o an idle control valve.

(IMG:style_emoticons/default/agree.gif)

The key is controlling idle speed with timing as Greg said. A bit of ignition trough to settle the engine in works quite well, particularly if you increase the map resolution a bit in that range. Note that while optional with a TB/plenum you really need to do this with ITBs unless you want a lot of plumbing complication.

Since you have a really nice air box, I would highly recommend using a Bosch TMAP (temperature/map sensor) installed in a boss for the barometric correction. They aren't too expensive, hide well, and are very robust. If you want to go really crazy... some motorcycle MAP sensors, 1 per cylinder, with a IC used to pull the max manifold pressures would give a really good input to speed density. From what I've seen, the failing of most ITB speed density is that a physical signal average (4 tubes from each manifold running into a plenum) is a) highly damped and b)biased downward so it's not really a true MAP representation. Someone used to make a board to do that processing, though I haven't seen one in years.



User is offlineProfile CardPM
Go to the top of the page
+Quote Post

Posts in this topic
bbrock   Going to Megasquirt   Sep 11 2021, 10:46 AM
BeatNavy   Brent, you'll enjoy the challenge and learning...   Sep 11 2021, 01:43 PM
Morph914   Brent, I will be watching this closely as I may sw...   Sep 11 2021, 02:13 PM
Chris914n6   I'd run Speeduino over MS as it's a newer ...   Sep 11 2021, 02:44 PM
JamesM   I'd run Speeduino over MS as it's a newer...   Sep 11 2021, 04:53 PM
Superhawk996   Just sayin' . . . . https://thedubshop.com/du...   Sep 11 2021, 03:10 PM
r_towle   Buy ITBs that look like carbs Buy manifolds with i...   Sep 11 2021, 03:22 PM
JamesM   Throttle Body? Given you already have the cool ai...   Sep 11 2021, 04:30 PM
930cabman   Throttle Body? Given you already have the cool a...   Sep 11 2021, 04:44 PM
JamesM   Looks awfully confusing. Is the Weber setup that ...   Sep 11 2021, 04:56 PM
Montreal914   Will follow this thread with great interest. :pop...   Sep 11 2021, 05:02 PM
GregAmy   I go to all the trouble to write this stuff up... ...   Sep 11 2021, 06:03 PM
bbrock   I go to all the trouble to write this stuff up......   Sep 11 2021, 06:41 PM
JamesM   Mario at the dubshop makes some awesome parts and ...   Sep 12 2021, 12:18 AM
GregAmy   And I have read ALL of it! In fact, I blame y...   Sep 12 2021, 09:57 AM
bkrantz   Brent, welcome to the club. You may make progress...   Sep 11 2021, 07:21 PM
bbrock   Brent, welcome to the club. You may make progres...   Sep 11 2021, 08:15 PM
Montreal914   In case you haven't seen/read my partial adven...   Sep 11 2021, 08:59 PM
moto914   Hi. Running Microsquirt with ITBs here. The kno...   Sep 12 2021, 08:47 AM
bbrock   @[url=http://www.914world.com/bbs2/index.php?showu...   Sep 12 2021, 10:49 AM
JamesM   [b]@[url=http://www.914world.com/bbs2/index.php?s...   Sep 13 2021, 04:46 PM
bbrock   I still think you are adding needless complexity ...   Sep 13 2021, 07:51 PM
JamesM   Sadly, the more complicated it looks, the more I...   Sep 13 2021, 11:07 PM
Superhawk996   Sadly, the more complicated it looks, the more I...   Sep 14 2021, 05:38 AM
bbrock   @[url=http://www.914world.com/bbs2/index.php?show...   Sep 15 2021, 08:08 AM
Superhawk996   I tried, but can't let this slide. . . . ...   Sep 15 2021, 08:41 AM
Montreal914   For ITBs, you have probably read that some people ...   Sep 12 2021, 12:25 PM
bbrock   Good to know about the MAP sensors. Looks like mo...   Sep 13 2021, 08:26 AM
GregAmy   Good to know about the MAP sensors. Looks like m...   Sep 13 2021, 10:28 AM
falcor75   I went the ITB route for my 2.3 but my car isnt bu...   Sep 13 2021, 11:14 PM
GregAmy   What I'm not happy about is the low idle at st...   Sep 14 2021, 06:00 AM
jd74914   What I'm not happy about is the low idle at s...   Sep 14 2021, 07:10 AM
ClayPerrine   If you don't have manifold vacuum at idle, but...   Sep 14 2021, 06:54 AM
VaccaRabite   James is the man, and I'd take his thoughts as...   Sep 14 2021, 08:13 AM
bbrock   @[url=http://www.914world.com/bbs2/index.php?showu...   Sep 14 2021, 12:05 PM
JamesM   [b]@[url=http://www.914world.com/bbs2/index.php?s...   Sep 14 2021, 01:08 PM
Montreal914   [b]@[url=http://www.914world.com/bbs2/index.php?s...   Sep 14 2021, 09:09 PM
bbrock   WOW! Really impressive! :worship: ...T...   Sep 14 2021, 10:36 PM
ClayPerrine   But... yeah. I think I'm going ahead with se...   Sep 16 2021, 06:21 AM
Superhawk996   Check out the MS3 Pro Module. Clay :yikes: ...   Sep 16 2021, 07:39 AM
bbrock   [quote name='ClayPerrine' post='2945887' date='Se...   Sep 16 2021, 08:24 AM
jd74914   But... yeah. I think I'm going ahead with se...   Sep 16 2021, 09:08 AM
Mike D.   Ahhh, yes! The beginning of another 7 year thr...   Sep 15 2021, 10:31 PM
jd74914   They're certainly right in terms of the poor s...   Sep 16 2021, 08:52 AM
Superhawk996   Modern injectors are objectively better. . . . I...   Sep 16 2021, 11:38 AM
bbrock   [quote name='jd74914' post='2945908' date='Sep 16...   Sep 16 2021, 05:00 PM
bbrock   An additional 800 miles of seat time in my car has...   Oct 9 2021, 08:44 AM
Superhawk996   - Do I need a crank sensor? To go full sequentia...   Oct 9 2021, 09:07 AM
JamesM   - Do I need a crank sensor? If you want to run...   Oct 9 2021, 04:53 PM
nditiz1   I have only seen the crankfire setup that McMark w...   Oct 9 2021, 01:15 PM
bbrock   I have only seen the crankfire setup that McMark ...   Oct 9 2021, 01:51 PM
Frank S   I have only seen the crankfire setup that McMark...   Oct 9 2021, 03:56 PM
ClayPerrine   Add a 36-1 wheel behind the fan replacing the spac...   Oct 9 2021, 04:56 PM
bbrock   This is all great info everyone! Looks like I...   Oct 9 2021, 06:17 PM
JamesM   You raise an interesting question about injector...   Oct 10 2021, 01:15 AM
bbrock   Okay, here's some fun with math. I calculated ...   Oct 10 2021, 12:20 PM
Superhawk996   I didn't check your math. I'm impressed th...   Oct 10 2021, 04:15 PM
bbrock   I didn't check your math. I'm impressed t...   Oct 10 2021, 04:18 PM
bbrock   Found a major error in my calculations. I accident...   Oct 10 2021, 07:03 PM
JamesM   Found a major error in my calculations. I acciden...   Oct 11 2021, 02:21 AM
bbrock   With larger injectors you lose some level of prec...   Oct 11 2021, 11:59 AM
jd74914   With larger injectors you lose some level of pre...   Oct 11 2021, 12:38 PM
bbrock   I'm not sure this is really a 'code' ...   Oct 11 2021, 02:08 PM
JamesM   Im just going to leave this here to give you more ...   Oct 12 2021, 12:33 PM
jd74914   Pulses of ~10 ms aren't too bad. But... I d...   Oct 11 2021, 03:00 PM
bbrock   Pulses of ~10 ms aren't too bad. But... I ...   Oct 11 2021, 04:04 PM
Frank S   Fuel Injector Size: https://thedubshop.com/pages....   Oct 11 2021, 03:49 PM
bbrock   Fuel Injector Size: https://thedubshop.com/pages...   Oct 11 2021, 07:45 PM
Frank S   I looked into the daughter board and you still ha...   Oct 11 2021, 10:55 PM
JamesM   It sounds like you really want to go with the 36lb...   Oct 12 2021, 01:17 AM
jd74914   I've looked at Mario's and a couple other...   Oct 12 2021, 07:18 AM
jd74914   Good info! I actually have a toothed cam w...   Oct 12 2021, 07:08 AM
crash914   Call Mario. Ask about the MAX EFI. will integrat...   Oct 11 2021, 04:06 PM
bbrock   Well no reason to stop this insanity now, so here...   Oct 11 2021, 07:24 PM
Superhawk996   You're becoming a real Geek. :lol: I've...   Oct 12 2021, 08:13 AM
bbrock   You guys are awesome! :trophy: I was reading...   Oct 12 2021, 08:38 AM
VaccaRabite   I worry that the larger picture of building an EFI...   Oct 12 2021, 10:22 AM
bbrock   I worry that the larger picture of building an EF...   Oct 12 2021, 11:10 AM
Superhawk996   Here's the view from my window today so I...   Oct 12 2021, 01:54 PM
JamesM   I worry that the larger picture of building an EF...   Oct 12 2021, 12:04 PM
bbrock   I worry that the larger picture of building an E...   Oct 12 2021, 12:35 PM
bbrock   Im just going to leave this here to give you more...   Oct 12 2021, 12:36 PM
KELTY360   Obviously, while the snow is on the ground you nee...   Oct 12 2021, 01:36 PM
bbrock   Obviously, while the snow is on the ground you ne...   Oct 12 2021, 01:57 PM
KELTY360   Obviously, while the snow is on the ground you n...   Oct 12 2021, 02:00 PM
bbrock   :chair: Don't be such a cynic. With all th...   Oct 12 2021, 02:31 PM
Superhawk996   BTW... :idea: see PM   Oct 12 2021, 02:37 PM
jd74914   That question was for the collective. I expected ...   Oct 13 2021, 07:24 AM
ClayPerrine   If you want distributorless ignition, there is an ...   Oct 13 2021, 06:28 AM
Frank S   Had a chance to check some of my data. With the 21...   Oct 14 2021, 09:58 AM
bbrock   Had a chance to check some of my data. With the 2...   Oct 14 2021, 05:49 PM
JamesM   Had a chance to check some of my data. With the ...   Oct 15 2021, 10:15 AM
bbrock   [quote name='bbrock' post='2952564' date='Oct 14 ...   Oct 15 2021, 06:21 PM
Frank S   Still not sure how much precision is being sacrif...   Oct 15 2021, 11:58 PM
JamesM   Still not sure how much precision is being sacrif...   Oct 16 2021, 10:56 PM
Frank S   And here how it looks like if you integrate the MS...   Oct 14 2021, 10:03 AM
bbrock   And here how it looks like if you integrate the M...   Oct 14 2021, 05:36 PM
Frank S   And here how it looks like if you integrate the ...   Oct 15 2021, 01:57 AM
bbrock   I've been wondering if there is an advantage i...   Oct 16 2021, 10:42 PM
JamesM   I've been wondering if there is an advantage ...   Oct 16 2021, 11:04 PM
2 Pages V  1 2 >


Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



- Lo-Fi Version Time is now: 12th November 2024 - 03:12 AM