FI & Full Tilt Performance

[Dale M.]

OK IF I want to go Megasquirt and get the most performance out of engine (used for Auto Cross Racing - 2180cc with dual Weber 44 IDF's)... What is going to be best TB combo?

The Mexican VW FI with dual port head runners with single TB in middle or a pair of throttle bodies (CB performance style) on short manifolds (injectors either in TB or manifolds) directly over heads....

Looking to get at least same level of performance the carbs give me.... Keeping in mind this engine see mostly second gear and works in a range from 1500 to 7000 RPM (no its not a typo)...

Anticipating using full electronic (distribuitor less) ignition also (Mega-EDIS)...

EFI is pretty new to me, only experience I have had is I got a FORD 5.0 EFI engine running for friend by chopping down harness from a MUSTANG and using most of wiring and engine sensor and ECU from the Mustang harness..... Do also understand fuel pressure/regulation/pumps/return lines etc..... Just not really sure which way to look for throttle bodies and where to throw the money....

Dale

[Vee Dub Nut]

We'll I'm a newcomer to the EFI scene.. I'm currently building up a Megasquirt/EDIS system for my 1915 using a German TB and plenum

I'm basing my opinions on what I've read and observed. If you are going to stay naturally aspirated, I would no doubt run CB's dual throttle bodies, or fab up your own ITB set up. I think the single throttle body would limit you quite a bit in NA form. Now if your looking to go forced induction, I like the benefits of a more simple single TB system and not having to deal with linkage or more complicated plumbing of the charge pipes.

I will run my system NA for a while, and I fully expect some performance loss compared to my dual Dells, but my longer term plan is to run a small turbo to make a mild boost fun street car.

[SUbuggy]

I'm basing my opinions on what I've read and observed. If you are going to stay naturally aspirated, I would no doubt run CB's dual throttle bodies, or fab up your own ITB set up. I think the single throttle body would limit you quite a bit in NA form. Now if your looking to go forced induction, I like the benefits of a more simple single TB system and not having to deal with linkage or more complicated plumbing of the charge pipes.

i completely disagree. in your words, "you are diving the car most of the time in second gear" that means part throttle is important. plenum and single TB all the way. better MAP signal, no linkeage headaches, better all around setup. If all out WOT is your thing, got ITB. How many OEM's today (engine that need to operate over a wide RPM range) have ITB's?

[Vee Dub Nut]

I'm basing my opinions on what I've read and observed. If you are going to stay naturally aspirated, I would no doubt run CB's dual throttle bodies, or fab up your own ITB set up. I think the single throttle body would limit you quite a bit in NA form. Now if your looking to go forced induction, I like the benefits of a more simple single TB system and not having to deal with linkage or more complicated plumbing of the charge pipes.

i completely disagree. in your words, "you are diving the car most of the time in second gear" that means part throttle is important. plenum and single TB all the way. better MAP signal, no linkeage headaches, better all around setup. If all out WOT is your thing, got ITB. How many OEM's today (engine that need to operate over a wide RPM range) have ITB's?

He's not talking about part throttle.. did you see the RPM range he wants to run in? He mentioned using a Mexican throttle body and runners... I could be wrong, but I think that's going to limit the breathing of a 2180 running @ 7000 rpm. It would be like throwing a stock carb back on it, you can only breath so much through that little hole.

[SUbuggy]

It would be like throwing a stock carb back on it, you can only breath so much through that little hole.

no doubt about that. My meaning of a plennum runner manifold assumes it would be properly sized for the engine, RPM range and intended useage.

[Vee Dub Nut]

Oh ok.. then I agree with what your saying. Having a properly sized plenum and throttle body would give you nice all around drive ability and performance. Just don't expect the german or mexican efi stuff to allow your engine to breath unless your forcing air through it.

[Dale M.]

OK... So even with using a LARGE throttle body (maybe a 65mm that Dave was was showing pictures of in another thread) with custom plenum and Mexican end castings its not going to give me the performance I really want..... So its back to dual TB's sitting right above head.... By the way linkages does not bother me, I do understand and can tune linkage.... That is the simplest thing going and people just don't comprehend how to do it....

Dale

[Tom Notch]

So, Two quick assuptions- 1-T1 cooling, upright, and 2- Dual TBs will fit in whatever you have this engine in?



Both single or multi throat would work for you. On an upright it's just harder to build a big enough clean system and fit it in the enguine compartment of a bug. Not impossible , just a lot more work than bolting on a pair of 44mm TBs on already ported manifolds (?) that are attached to your engine.

Plus if you use a 44mm TBs you just gained 10-15% in potential flow (same size as a somewhat typical vent in a 48 IDA........). While spendy, I'd look at Jenveys and TWNs replacements for IDFs which have injectors in them, and basically bolt them on and add your wiring and plumbing.


Sounds like what I would do with zero hesitaion.

[Dale M.]

This setup would be in a MANX style dune buggy so "space" is not a issue....

Sorry I forgot to mention that....

Dale

[SUbuggy]

Both single or multi throat would work for you. On an upright it's just harder to build a big enough clean system and fit it in the enguine compartment of a bug. Not impossible , just a lot more work than bolting on a pair of 44mm TBs on already ported manifolds (?) that are attached to your engine.

agreed. never gave thought to the "logistics" of your exact installation.

Plus if you use a 44mm TBs you just gained 10-15% in potential flow (same size as a somewhat typical vent in a 48 IDA........). While spendy, I'd look at Jenveys and TWNs replacements for IDFs which have injectors in them, and basically bolt them on and add your wiring and plumbing.

kinda disagree here. at a certain point, the TB is not the "restriction" in the inlet tract anymore. you could bolt up a 200mm TB and you are not going to flow any more air since ultimately the intake valve and port become the airflow restriction.

look at NHRA pro-stock. all run 500cubic inches making near 1000hp with a single carb and single plane "plenum" manifold. somehow they can get enough air from that to flow 8500RPM..................

if you really want to go dual TB, CB has 44 with bosses right in them............

[Fiatdude]

I'm going to use a single TB on my car -- got it from pick-a-part off a GM V-6 alot cheaper than the CB stuff

[j-bro]

How many OEM's today (engine that need to operate over a wide RPM range) have ITB's?

BMW does on their M engines. I guess they don't know better

[Tom Notch]

SUBuggy, you overlooked the word "potential" I used. My intent was that the TB will maybe be bigger than the rest of the intake track. I did not mean to imply that bolting on the TBs would magically increase flow. I know much better than that .

[SUbuggy]

BMW does on their M engines. I guess they don't know better

yes, bmw has used these type of intake with great success. ( i own an e46 m3). but BMW has never been known for making things simple. if you compare a BMW v8 to an american V8, you will have to admit that the American 'antique' V8 using pushrods, single cam, single TB intake puts up some pretty impressive numbers compared to other far more elegant V8 designs. the point is, single TB designs are far more prevalant today, and can make good power and very drivable.

SUBuggy, you overlooked the word "potential" I used. My intent was that the TB will maybe be bigger than the rest of the intake track. I did not mean to imply that bolting on the TBs would magically increase flow. I know much better than that .

yes, please don't think i was preaching at you, i have no doubt you you are aware. i was trying to get the point out to other reader who may be mislead.

[raygreenwood]

Yes...there is absolutely nothing simple about that BMW ITB system. The production standards on each of those TB's...and the ports and valves behind them is VASTLY higher and more costly than the standards on any single TB....to keep from having to synchronize airflow volume for each TB....or worse...having to have individual MAP sensors on each TB.
Also....the actual air cleaner and hood assembly is actually part of the metering system for those TB's.

They didn't save a penny on R&D and testing that they would have had to spend developing a plenum based system for that engine.....they simply passed it on to each end user in the elevated cost of machining and QC for that set-up.

The fact that it does perform as well as many plenum systems....means that it was actually pretty smart for BMW. Less testing time and up front cost to bring it to market....and you the buyer foot the bill for that hardware on each car you buy!
Its elegant...and no one ever said BMW was stupid. But it is nowhere near as cheap as a plenum system and casting as far as actual production costs are concerned.
The cost of a plenum system is in the devlopment and tuning. Hopefully you are slapping that plenum system into something you are making 100,000+ units of.

Ray