Survey Thread - Carbs or Megasquirt

Benji's New Setup

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    26
bwalvoord

bwalvoord

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I've been wrenching with this decision over the last week and now that I've actually spoken with most of the engine experts mentioned in these halls (Don, Jesse (no longer at dynotech), Paul Burke and others), I'm still left with the basic decision. I don't know where else to turn so what better place than those that have already made this decision. But first, a little more background on me. I'm 38, run a business, 2 small kids, wife is an OB/GYN who works fulltime so in other words, I don't have a lot of free time and when I do, I'm usually getting up at 4am to run insane miles training for my next ultra marathon. OK, so here goes...

Triples or MegaSquirt?

I definitely prefer the look of the webers and the hot-rod feel of it. On the other hand I need to be able to drive it with the AC on (it's hot in SC pretty much year round in this car) and will want to be able to jump in it whenever I want (as long as there is no rain in the forecast!). I am also more comfortable on a laptop than I am in the engine bay (although the line needle is slowly but surely starting to even out thanks to this group).

I suppose the deciding factor could be whether someone wants the triples I already bought (still in the same box, same price).

In the end what I want is a decent pull and throaty exhaust. I drive an M3 now and don't have the testes to really put the hammer to it but man does that sound nice when you punch it.
 
As you know from your earlier post I have triples and love them for the reason Andrew mentions plus I am all about the induction noise which provides a glorious soundtrack to the coupe driving experience. I don't know anything about megasquirt but it's probably a lot more efficient etc. but without the intake sounds. Also when I mash it under an overpass or with buildings around the noise echoes back and sounds even better. The pitch of the wail also indicates the engine's state of tune. Gas mileage bad in town, ok on highway.

As far as a/c, I run mine in the summer with the Webers, you can keep the idle at 1000 or so to compensate for when the compressor comes on (a rotary compressor will drop the idle less than the stock York) just like you would with Zeniths.

I added a solenoid to my throttle linkage which maintains the idle when the compressor cycles on and off which has worked out pretty well.

IMG-20121027-00063.jpg
 
How about running the carbs with mapped ignition? Mine starts an idles from cold with no coughs and pop's and I'm sure you could add the compressor control function. Best of both worlds?...I think so!
 
Thanks guys. Just got the call from my mechanic and the machinist. Rods need to be shortened and new bearings. Sounds like I am officially off the fence. Now to find that M30B35 and let Paul B. cook me up something special.
 
Sounds like you need the convenience of a modern car in an old style

Sounds like you need a reliable car first, a classic second, and a hot rod third. I'd vote for a stock b35 3.5 transplant w Motronic 1.3.
The more stock/ modern tech the better. Friends who've successfully raced BMWs for decades say Megasquirt on modified engines leaves carbs in the dust. At the opposite end of the spectrum, I put period authenticity ahead of comfort and breaking down 100 miles from home because I don't drive the old cars if travel time is a concern.
 
Did you use the 123ignition? I've read about their products on another forum but have not heard of anyone using it.

Polariscsl said:
How about running the carbs with mapped ignition? Mine starts an idles from cold with no coughs and pop's and I'm sure you could add the compressor control function. Best of both worlds?...I think so!
Click to expand...
 
What about a custom Di system sing

custom individual throttles and FI manifolds with long velocity stacks? That would give the side draft intake roar with the advantages of FI. Or, a period correct slide throttle race FI system with mega squirt
 
For hassle free running go for FI

DCOEs look good, sound good and generally perform well if set up right

HOWEVER

The idle mixture can and does go out of tune, and the big one is the balance between the carbs, not hard to adjust if you know how and have the time and the syncro gauge to do it, but it is something that needs looking at from time to time.

With the carbs you need to check and adjust the following depending on how much you use the car???

Fuel pressure (DCOEs need lots of volume but at low pressure, about 3.5 psi is good, Too much pressure over whelms the float valve and then you end up with fuel dripping out of the carbs, great for engine fires, (don't ask how I know this!))

Fuel float levels

Carb balance (between all three)

Idle mixture


and if you have to ask your self again.............

MODERN CARS HAVE FUEL INJECTION FOR A REASON

Moving on from this you can have the best of both if you want to spend some more money

FI with individual throttle bodies will give the sound you want and the ease of use of FI


My 2 cents worth
 
trips

my 3.5 has motronic 1.3 with a warr chip, but i still vote for the trips - you just gotta love the previously mentioned 'wow' factor when you open the hood.

BUT... my car is a driver, and i really do appreciate and enjoy the dependability of fi - cold starts, idle with ac on, etc. i really missed the induction roar though, so i swapped out the stock air filter for an aftermarket cold air intake, and presto, induction roar back to 80-90% of carb sound.
 
A marathon runner does not need reliability, you can run farther than a tank of gas will get you. With your wife a full time M.D. now that everybody is insured you could afford a CSL BAT.

I vote for carb mostly because I do not know what a Megasquirt is, and it sounds cheesy.
 
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I was in Vegas last year trying to smog a 365 gtb 2+2 with 6 webers and the Daytona
cams and that was the end for me. I will never touch a carb again.
Too many parts, too many variables.
 
+2 for MS (both my Bav and Coupe will have it). I want consistency/reliability, efficiency, and performance. When I'm driving the hood is closed so nobody can see it. When I stop, only the gear heads want to see what is under the hood. As a gear head myself, I like the idea of an antique fitted with modern FI.

An M30B35 w/ MS really runs strong.
 
And with the right tweaks a b35 will look like a vintage FI setup even with Motronic, that is why I am going this route. Use the older log plenum and C runners not the normal b35 vertical plenum.
 
You have to want triple webers to want triple webers.

I can't tell you what you should do so maybe the question is what would we (the brotherhood) do in your place.

The CS/CSi was offered in both flavours - Zenith carbs and D-Jet EFI - never triple webers unless you include the tuner cars that were largely CSL's. So if you are even considering triples you have already crossed out of "correct and original" and into the fun zone of the privateer where anything is allowed. The fun zone also includes the individual throttle bodied CSL's with the Kuggle... mechanical fuel injection's found in the BAT race cars and others but that is serious $$$$.

The triples look and sound gorgeous and once set up throw a lot of sound and fury (and gas) at the problem and are "era" correct. Great stuff. Tweakable and tunable (in a relative sense) with distributor curve modifications, jetting combinations and hotter cams. Racer stuff. The sound at either end is intoxicating.

The D-Jet in it's native state provided operational advantages but not the same level of sensory excess as hot triples and was not modification friendly because of the fixed nature of the ECU controlling the whole thing. For that you need programable engine management of which MegaSquirt has gained a lot of traction due to cost and an open community approach to it's programming and development. Hot Damn - now we can tune the D-Jet in ways that the triple carb can only dream of - bore it out, hot up the cam, bigger valves - anything can be brought in and incorporated with a lap top without compromise.

But what about that induction noise? That sound of a tornado threatening to suck small children and dogs off their feet and into the engine. What about that triple weber eye candy that is part of the carb magic? That Swiss watch complexity with everything (eventually) moving in harmony (hopefully).

For that you need the ultimate solution to the induction question. A set of S38 individual throttle bodies with velocity stacks and cookie air filters on each one. All the sound of the Wagnarian heavenly chorus, the visual splendour of the pipe organ at Winchester Catherdal and the power of the large Hadron Collider. Perfection has been reached. The next generation of the triple webber has arrived. And it starts in cold weather, idles to the limits of the chosen cam and as drivable at either end of the spectrum like a.... well... an m5.

You will need something to run it so the MegaSQ (or something like it) will hide in the background discreetly allowing you to control the whole thing. Don't worry, nobody needs to know because you can't see it and once it is set up you'll never need to touch it again and it will never go out of tune.

You have to want triple webers to want triple webers. You have to want that look and sound and the smell of gas and all those moving parts and the tuning that goes with it. And that is great and I will look on in admiration at the perfection of that vision.

But I vote EFI.

Please don't hate me. Please.
 
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Decoupe has the absolutely modern equivalent of the side draft solution. Cool looks and big induction noise. First saw this set up on Cosworth YBs, killer power but they looked and ran great with side drafts as well.

Tough choice. For tune-ability EFI has the clear lead, better power. But....I've had Weber side drafts on my Alfa, Lotus, Cortina, and 2002. Something simple and sweet about dialing them in. Hand built machine / hand tuned. Maybe not perfect but with soul.
 
I have truly become smitten with this car and this decision. I can't tell exactly how many times I woke up in the middle of the night wondering which route to go. When I was on the phone with Paul he mentioned an S38 head but that was in the middle of a 30 minute treatise on the flexibility of the M30.

So, the fact that I cannot settle on the triples means i should go a different route and Decoupe has put forth a very elegant solution.

Thank you.

To that end, the trips will most likely be for sale if someone wants them. Oh, and the oil pump from DQ.
 
Related question - I guess from all the positive comments on here that megasquirt is well thought of in the US? In the UK you are hard pressed to get a tuning outfit to agree to map one based on the high failure rates on the rollers.....
 
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