1.8 head on 2.0 block or 2.0 head + block w/ big pistons?

[bradartigue]

Your limitations of L-Jet are all absolutely wrong. It's not relevant perhaps, I am absolutely not trying to dissuade you from your goals. I read through this post and am almost begging you to do some reading and understand how things work. Many an owner has spent thousands on induction/head work/engine work only to end up with a car that performs about as well as stock...because they never bothered to understand how the car performed in the first place.

[TimpanogosSlim]

Your limitations of L-Jet are all absolutely wrong. It's not relevant perhaps, I am absolutely not trying to dissuade you from your goals. I read through this post and am almost begging you to do some reading and understand how things work. Many an owner has spent thousands on induction/head work/engine work only to end up with a car that performs about as well as stock...because they never bothered to understand how the car performed in the first place.

Maybe you can explain then? Are you saying that the performance can't be better, or that somehow the lampredi twin cam makes power differently than other internal combustion gas engines?

[bradartigue]

I'm not saying either one. I'm saying you've made quite a few broad statements here, about the fuel injection system, about carburetion, about general induction, that are simply inaccurate. I'm saying the point at which you are starting is misinformed, and a big problem enthusiasts have with any car is tempering their enthusiasm. I'm also saying that you appear to be jumping from a fundamental misunderstanding of the way the car performs to some vague concept as "peak performance." What is peak performance?

You will not define performance the same as I would, and everyone has an opinion as to what that means. What do you mean by performance? If you can define that - set some goals - then the kind of assistance you'll receive will be much more meaningful.

[TimpanogosSlim]

what i meant by "peak performance" was in relation to how well one can reasonably expect a factory-fresh 1981 spider 2000 to run. Or even the same plus some tweaking.

Which is not something i am interested in duplicating, for philosophical reasons.

Have i somehow misunderstood the operating range of a bosch vane air flow meter? The BMW and Porsche guys with L-Jet seem to get rid of it at the earliest opportunity, particularly for forced induction upgrades.

I'm pretty sure L-Jet predates wide-band o2 sensors, so it's ability to adjust the mixture based on that sensor's reaction must necessarily be somewhat coarse compared to modern systems.

It's pretty frustrating to be told that one is operating from a position of ignorance and then not have any corrective information offered.

[bradartigue]

It's pretty frustrating to be told that one is operating from a position of ignorance and then not have any corrective information offered.

Equally frustrating to be asked for help while having to read criticisms of the car written from ignorance. The only time you stated a goal was in the most recent post - otherwise all you've done is say you want "peak performance." There is nothing to correct, you don't know how what you had worked when new, you don't know what you have, and you didn't have a goal. Now at least you have something to work from, 50 posts later.

A few things to consider -

A "factory fresh" 1981 Spider was a pretty zippy car. If you have the opportunity to drive one that is set up as stock then you might want to - but it's not ever going to be the equivalent of a modern car. It has 102 HP and always seems to be about 10 HP short of perfect. The least expensive and most reliable way to address this is through a compression increase, and 9.2:1 pistons do a wonderful job without much of a sacrifice. It makes it fun to drive.

No Spider has a transmission that can handle a lot of HP. If you are the kind of person who likes to drop the clutch and have 150 HP at your command then you should buy a couple of transmissions and a box of transmission parts.

In my opinion any FI system is better than any FI carburetor setup - but you have to deal with a lot of electronic and fuel related things to get an FI system sorted on a non-FI car. However it will take a long time, months probably, to get it right, and I'm too impatient, so I'd rather make a high compression engine with a very nice head and a huge single or dual DCNFs (IDFs if you prefer but I like DCNF's tuning range). You could get all of this done in a couple of weeks and be hovering in the 130HP range, more than a Spider off the track would ever need. You'll also save a few thousand.

I know a whole lot of BMW and Porsche people who run some very, very high performance cars with L-Jetronic (and K-Jet for that matter). The AFM installed is sized to the car as delivered by the factory - in the case of the FIAT, sized to a 2000cc engine. Because there is no computer if you do a bunch of modifications you are going to have a greater demand for air than the AFM has capacity for. You either get a larger AFM or you choose another route. The result is a rich running car, if it ever fires the injectors long enough to go beyond WOT (which I do not think it will). Peugeot drivers note a piggyback ECU that takes care of this - but at some point no matter how much air you are jamming in there, turbocharged or otherwise, the system will be at max potential. At this stage you have your megasquirt crowd or, as FIAT did, supercharge it and put a Weber carburetor (Volumex).

I actually think in your case, with the modifications you are considering, you should look at supercharging with factory parts. I don't think the cost or pain-in-the-ass factor will be any different, but you'll have a VX Spider. I would put Megasquirt second on my list after I priced it/compared them all out. Complete VX setups aren't so rare and you won't be fabricating anything. The badass factor would be remarkable.

See, I'm not all evil.

[RoyBatty]

Hey Brad,
Where are you sourcing the VX components?
I'd like to look into it further.
I'm picturing a dual IDF, supercharger setup.
Thanks.

[TimpanogosSlim]

running rich most of the time to avoid running lean some of the time is the sort of compromise i'm not really interested in.

and we're talking about the same limitation of the AFM. altering the configuration so that the system behaves as though there is more air moving through it seems like a hack to me.

"bigger" afm sounds like one way to do it, while adjusting the mechanism in the existing afm would be another. I've seen people do this with denso/toyota systems, the other direction, to lean out the mixture slightly. of course in later systems that have some adaptive code in them, it doesn't work for long.

But apparently it doesn't matter that my interest in a megasquirt build is academic. That it's something i want to know how to do. Because it interests me, and because i see future applications in hobby projects that have nothing to do with old fiats.

If i choose an easy path, it'll be naturally aspirated with the IDFs i already own.

I don't recall saying that i was trying to achieve "peak performance". I'm pretty sure i said that the peak performance of the stock 2000 EFI system is something that i am not interested in retrofitting into my '77.

To sum up:

Technical challenge of retrofitting, bandaiding, and maintaining L-Jet: Not interesting. Rather watch reruns of The View.

Technical challenge of implementing megasquirt: Interesting.

Technical challenge of tuning up a four barrel carburetor system: Less boring than L-Jet.

I'm sorry if that offends your sensibilities.

[bradartigue]

Hey Brad,
Where are you sourcing the VX components?
I'd like to look into it further.
I'm picturing a dual IDF, supercharger setup.
Thanks.

From Europe or from Obert. Look for 131s that had it. Maybe Csaba can help (I've never asked so I don't know). The supercharger from the factory uses a carburetor (Weber DCD I think), IDFs won't work because the snorkle runs across the motor and into this weird intake manifold that integrates the supercharger and the carburetor inputs.

[bradartigue]

I'm sorry if that offends your sensibilities.

If you already knew what you wanted, why are you asking the questions in the first place?

There is nothing more frustrating than trying to help someone who knows all the answers. I won't make that mistake again! As far as being offended, I couldn't care less, I just know that about 1 out of every 1,000 projects like this ever see the light of day. I'd rather see the cars on the road.

[TimpanogosSlim]

I thought i asked a fairly reasonable question between two options, and got told that both of them are wrong.

[ORFORD2004]

I just know that about 1 out of every 1,000 projects like this ever see the light of day.

So, I own a very rare spider

[RoyBatty]

Thanks Brad,
On reflection, I suppose the supercharger negates any benefits of the dual carb setup so I can live with a single carb when the time comes. All the images I've seen of the factory setup are all single carbs.

For the new guys,
Brad is a personality that like seems, like me, to not see a lot of grey in the world. He can be a bit gruff and opinionated and he has earned that right IMO.
Look thru the history of his posts on this forum and you will see that he has been an invaluable resource.
If you feel he is trying to offend or had been offensive, well, that's just how it goes sometimes.
As I have told some friends in the past, you don't have a right to not be offended. And yes they are still my friends.

[bradartigue]

I thought i asked a fairly reasonable question between two options, and got told that both of them are wrong.

Whatever, good luck.

[bradartigue]

I just know that about 1 out of every 1,000 projects like this ever see the light of day.

So, I own a very rare spider

You own a very rare car. It is no small effort to put in megasquirt, especially when the prevailing sense is "it can't be done." So don't LOL - it takes a ton of work to get these cars running correctly and un-screwing all the PO "enhancements" - much less to install an EFI.

I tried to make a point here and failed. Won't be the last time. I have this notion that if you do not understand how things work you cannot improve them.

[ORFORD2004]

So don't LOL

I LOL because it's very fun to drive.
And it was not that bad to install. At least for me.