Intersting observations on FI vs IDFs

[vandor]

Some of you know we have been struggling to get good power out of Jeff's (sptcoupe) 124 Coupe. It had decent power, but it was making max power around 6000 rpm, so we knew there was more to be had. The engine had programmable fuel injection with individual throttle bodies, so we really wanted this engine to sing
We went through everything, intake, exhaust, head, cams, etc, and could not find the reason why it was not making power on the top end.
Since Jeff loves Weber IDFs, as a last resort we converted to 44IDFs. Well, the power is back! Even with the manifold not ported, the engine makes 4 more hp, but more importantly, the power stays on until 7000 rpm! Before it would steeply drop over 6000 rpm.
The wider powerband makes a huge difference, the engine revs to 7500 rpm easily, and wants to go on! Once we port the manifold we expect that it will make even more power.
I would not have thought that this would happen, as 40mm throttle bodies have no chokes, and should flow better than 44IDFs. I do not know if we were up against some sort of wave interference, or why this happened. We even tried two different types of inlet horns with the TBs.
At least we are on the right track

[divace73]

interesting, could it have been a fuel supply/injector limitation?

[sptcoupe]

We have had a lot of help and good advice from many folks very knowledgeable in FI trying to solve this issue. We have had three sets of cams in there, two different heads, two differeent exhaust headers, different sized injectors/fuel pressure combos, three intake manifolds, including a sweet custoom version from Mark that tilted the TBs 22.5 degrees (won't work on IDFs - damn!), chased dozens of potential electrical issues, and made over 185 dyno runs (and used two dynos to compare!), and did at least 10 disassemblies to carefulyl and painstakingly measure and record every change - all of which were done one at a time in the last 17 months. And lets not forget the hundreds of hours doing over the road tuning using at least three different wideband sensors refinements .

The fact is, we never got it to make power past 6000 rpms, and it never really ran smoothly. I firmly believe that when you get into performance cams (40/80 or stronger) and TBs, the number of variables is infinite, and while you can get a TC to make decent power and run reasonably smooth if you are happy spending the time programming, the cost vs benefit is way out of wack, and I am not convinced - dyno verified -that you will ever get all the potential out of your motor. I have spoken to a lot of helpful souls, and they all seem to hit that 6000 rpm wall, and what I hear too often is "....I have it running real well, but there is this little flat spot, or this electrical issue, etc. And I learned form the over 185 dyno runs that when you think you are making really good power because it is reasonably smooth and revs to 7000 rpms OK, you probably are about 20 HP shy from what you think the power is.

We got slapped the IDFs on (only change from the last run), got about 144 RWHP, and hadn't even ported the manifold, and the jetting was way off. I managed to improve the AFR ratio a bit by playing with floats, etc, and it truly screams to 7500 rpms. When we port it and get it jetted correctly, we'll be back to the dyno and report again. My guess it will be an honest, dyno'd with zero correction 148-152 RWHP.

My take after this very painful experiment is that you should spend your money on all the things that make your engine more powerful (porting, headers, cams, CR lightening, balancing, rods, etc), not on the expense of TBs, management systems and custom pieces that come with a conversion, and put on a set of 40 or 44mm IDFs and have a very powerful, smooth running motor you can drive and enjoy.

BTW, the TBs, intake system, manifold and headers are all for sale.

[baltobernie]

Huh Who woulda thought?

I'm sure you will be posting all the particulars (and offering the components in your store ) once you're satisfied with the ultimate output. Can't wait! No, really, I can't wait! Are you running 40/80 cams? What cam timing and clearances?

[spiderrey]

Thanx 4 the info. Im glad Im on the right track. Went from 40,s to a single 38 which ran very well and now with 44,s. Always wanted tb,s or fuel injection, but now see its not for me.

[stonebike]

Have you people said any of this out loud and listened to yourself?

Carburetors are not as good as electronic fuel injection. Maybe it never worked right for you, but Ford, Honda, GM, Toyota, BMW, Mercedes Benz, and everyone else that employes an engineer, use electronic fuel injection.

I'm sorry to hear that you never made this work, but really, it's not the technology that had the short fall, it's the implementation. Please don't make people gun shy, I want there to be someone to work out proper fuel injection for these cars with better than the OEM system.

[divace73]

What type of ITB's were they?? And out of curiosity where was the injector located, close to the inlet port or further away?

[fiatfreak]

Amen to that. Not to dis on carbs, I had IDFs on my Spider before I changed to FI, but they can't adjust to the variables like FI. I've converted all my Fiats and Lancias to FI, all with modified performance engines. Try driving at altitudes varying by 4000 feet with a carbed car and you'll appreciate FI.

Have you people said any of this out loud and listened to yourself?

Carburetors are not as good as electronic fuel injection. Maybe it never worked right for you, but Ford, Honda, GM, Toyota, BMW, Mercedes Benz, and everyone else that employes an engineer, use electronic fuel injection.

I'm sorry to hear that you never made this work, but really, it's not the technology that had the short fall, it's the implementation. Please don't make people gun shy, I want there to be someone to work out proper fuel injection for these cars with better than the OEM system.

[vandor]

Carburetors are not as good as electronic fuel injection. Maybe it never worked right for you, but Ford, Honda, GM, Toyota, BMW, Mercedes Benz, and everyone else that employes an engineer, use electronic fuel injection.

Let me translate: anybody that has millions to spend on development, uses EFI. Also, most stock FI systems measure airflow directly with an airflow or airmass meter. If there was an aftermarket FI that did that, then it'd be much easier to tune for hot cams.
The main problem is that with individual throttle bodies and hot cams the vacuum signal is pretty much useless, so all one has left if TPS and RPM for tuning, so a lot of precision is lost.

I agree, in general FI is better all around for economy, smoothness, emissions, power. However, here we had one objective, to make the most power with a Fiat TC, and within that context IDFs stand up well to FI. For what it's worth, a well tuned set of IDFs will have just about the same smoothness as FI. People who say that IDFs have a stumble, rough idle, etc, just have not spent the time to tune them.
bye,

[vandor]

> I'm sure you will be posting all the particulars (and offering the components in your store

Yes, sort of, actually we have something bigger coming Most of the components are available now, but they are special order, meaning they get made when someone orders them.

> Can't wait! No, really, I can't wait! Are you running 40/80 cams? What cam timing and clearances?

We were running 42/82 cams, but switched to the Guy Croft 3A cams. The GC cams have a lot more area under the curve that the 42/82s, and actually idle better. We run then timed as specified, meaning we have not retarded or advanced the timing from Guy's specifications.
bye,

[vandor]

interesting, could it have been a fuel supply/injector limitation?

Then if would have gone lean toward the top. That was not the case. We actually tried two different injector sizes, just to see if it would make a difference. It did not, once mapped the car behaved exactly the same with one set than the other.

We also tried different fuel pressures, and also running with a rising rate regulator, or not.

[manoa matt]

Csaba, you should encourage the naysayers to read out loud all 7 pages of the thread on the Guy Croft forum: http://www.guy-croft.com/viewtopic.php?f=4&t=2423

See if they can find the short fall in the implementation that the most knowledgeable Fiat/Lancia gurus and tuners could not figure out. I don't even claim to understand half of that thread, but learned a thing or two, and appreciate your efforts. I'm pretty sure they will appreciate your efforts too if they decide to read it all the way through.

[stonebike]

MoTeC supports adaptation to many kinds of air flow meter or air mass sensor. Also, there are many ways around using a MAP sensor with ITBs and big cams. Vacuum canisters are used by many as a way to filter the wave pulses and give a steady reading.

[So Cal Mark]

why are you so confrontational? Sometimes experiments don't produce the desired results, and there is as much to be learned from that as one that meets expectations

[sptcoupe]

stonebike. My name is Jeff Scheferman, and I am the guy who is the owner, who paid the bills, talked to many experts to select components and a system that are/is designed for highly modified engines so that they had a better than avearge chance of working well together, tried many different components, listened to dozens of suggestions from other FIAT folks with significant FI conversion experience, and yes, tried many of the (very well known) solutions such as vacuum cannisters (2 designs, in fact) to manage wave interference, and used all the (very commonly) known ways to get around using the MAP sensor for ITBs and big cams (duh!!), especially since all those not-so myterious options were built into the sytem that is designed to accomodate ITBs and big cams.

I am also the guy who also insisted on uncorrected dyno runs and post-build disassemblies to make measurements that were real and accurrate and not subjective to be sure we were being honest with ourselves and the folks who have followed this project, And it was me who approved switching out major components, one at a time, to make sure we had made our best effort to deal with all the variables that were limiting the engine's output. We even had some custom designed components made at the suggestion of some really experienced FI guys to deal with the main issue of the power peaking way too early for this particualr engine build (like Mark's tilted intake manifold, different cold air induction systems, etc).

I also am the guy who willingly and in great detail chronicled all the mods on this engine on this and another forum, posted pics for skeptics like you, provided real dyno results and the real cost of this "epic failure" so that others in this extended family who are making the FI conversion could benefit from this experience. So this is my epic failure, 100%. Did I forget to say my name - Jeff Scheferman. Is that "owning up" enough, or need I keep going?

I am no stranger to FIAT TCs, having built my first performance motor in 1973, and many dozens since then. And let me clearly state that FI is better than carbs. To disagree is a fool's argument, and what is apparently obvious to everyone but you is that if I didn't truly believe that, I clearly would not have stayed with this effort for as long as we did and at such a ridiculous cost. But try as we might, we could not get it to make power beyond 6000 rpms, and that was way too low for this particular engine. It actually ran pretty well at the end and made decent power, but I couldn't justify giving up another 1500+ rpms of powerband after investing in all the performance components required to let the engine breath and be reliable at very high rpms. Why would I do that, when I knew we could get more.

The reason I shared this epic failure here and in other places is so that the average guy on this forum, with a limited budget and maybe not much experience, and limited or no access to a dyno, is fully aware of the infinite variables you will have to deal with to benefit FULLY from your investment in the components and development of your ITB FI conversion. Note I said benefit FULLY. I suspect you can readily get a really decent conversion with all the benefits of FI with a plenum design, but even then to get your money's worth, you will have to work at it pretty hard, and unless you are willing to put it on a dyno and get the real outputs, you may never fully get your money out of the investment.

So maybe my biggest error was sharing this "epic failure". So I'm done doing that. For those of you who want to know more and learn from this experience, you know where to find us and we will gladly do all we can to give you the benefit of this project to make your's more successful. For the rest of you, call stonebike and MoTec. Oh, and don't forget to call the engineer who designed your TBs, and have a lawyer teed up just in case someone decides to sue someone if it goes poorly. Geez.

And lest it be lost in all this noise, the only change we made before the last dyno run was to quickly install poorly jetted IDFs on a non-ported manifold. We got more HP and it pulls like a banshee to 7500 rpms, and I am sure it make HP to 8000 rpms before the rev limiter kicks in, but we'll wait until we have it properly jetted and the cam and ignition timing optimized.