FI & Full Tilt Performance

[Redline Weber]

Many times I have stated that it is just fine to "GUT" a carb'e (remove Choke & Aux Venture), then fit a port injector into the manifold OR air filter top cover.

This could save some hard earned cash or create "stealth" injection.

I do like "stack" (ITB) injection as I can read an increase in port pressure from the ram effect/pressure wave effect.

The "supercharged" N/A pressure increase (measured) CAN BE OVER 1.5 .lbs boost.

Lance

[miniman82]

That's true, I've heard from Eric that his manifold pressure during a run is frequently higher than ambient due to the ramming effect. You might call it 'natural supercharging'.

[SUbuggy]

That's true, I've heard from Eric that his manifold pressure during a run is frequently higher than ambient due to the ramming effect. You might call it 'natural supercharging'.

yes, and for a drag car that runs WOT all the time, tuning the stacks for optimum WOT will affect driveability the rest of the time.
I thought the orginal intent was to find an intake setup that works best from 2-7k, AKA part throttle.

[Eaallred]

That's true, I've heard from Eric that his manifold pressure during a run is frequently higher than ambient due to the ramming effect. You might call it 'natural supercharging'.

yes, and for a drag car that runs WOT all the time, tuning the stacks for optimum WOT will affect driveability the rest of the time.
I thought the orginal intent was to find an intake setup that works best from 2-7k, AKA part throttle.

Considering that I run an FK-89 cam, my engine runs great at part throttle and cruising with ITB's. Overall, I feel an ITB intake setup is superior all around, EXCEPT that you have throttle linkage. It would be nice to get rid of that. But then again, I don't really have any issues with it coming out of adjustment so not too big of a deal anyway.......

My car cruises fine, and at WOT, yes, I get positive manifold pressure. I've nailed 91KPA when our ambient air was 84KPA. Converted it comes to 1.01psi of 'boost'. About 8.3%. It's good, but i've heard that Pro Stock cars are in the neighborhood of 20%. That's got to be the result of a LOT of R&D time!

Oh yea, i'm running RedlineWeber 50mm IDF patter throttle bodies.

[raygreenwood]

This is actually the same effect you get with a plenum system on the runners. At a certain measuring point and down to the valve on a runner for a plenum you almsot always get pressure readings slightly above atmospheric. The principle is identical to stacks.
The difference in runners versus stacks is that the entrance to the runner (as compared to the stacks) is usually (but not always...it varies by design).....less efficient on the runner than it is on a stack. Though this reduces the overall flow ability of a runner....the normal runner which is usually quite a bit longer....usually has much higher air velocity at the valve than a shorter stack of the comparative same shape.

And by that token...just like a runner, if you have a long enough stack...you will get that higher velocity as well. But a set of open stacks without a plenum ....would largely be undrivable oon the street. I'm talking like 18" to 20+ inch tall stacks...which is what you would need to match the port velocity of a runner on a plenum system.

The plenum serves the purpose of charge filling AND feeding the runner openings at a controlled enough rate to not stall velocity at WOT. And....that impedes maximum flow....but gives the greatest range of drivability and great atomization at the port. On most runner and plenum systems at WOT you see higher than atmospheric pressure (for example on type 3 and 4 plenum systems).....from about the start of the bend to the port. Lower than atmospheric starts just above the bend and increases to the plenum. Ray

[SUbuggy]

My car cruises fine,

sorry, i do not find this to be a "scientific" approach. just because it "feels fine" does not mean that there is not improvment to be had. What does your torque curve look like? Is it as wide/flat as it "could be" without sacrificing top end? it is the same type of think that has some people still running points, because "it works fine".

[miniman82]

You missed the point completely- it's a race car.

So yes, 'it feels fine' is enough for Eric.

[Jadewombat]

Those who do not autocross--do not know the cheap thrills. I scrub the rubber off the tires and kill cones on my Mercedes C300 Sport whenever I can.

It sounds like you're set on using ITBs, some inspiration?/examples for you:

http://forums.vwvortex.com/zerothread?id=4591572&page=2

[Dale M.]

I seem to be leaning towards ITB's..... I have a set of trashed Weber 44's (water damaged) that would make throttle bodies but then I have to use the manifolds that have injector bungs in them.... This especially does not appeal to me and I don't particular like the designs of the "carb" application manifolds I have seen (CB Performance) .....
Also the idea of $500 to $600 for a set of TB's is almost stupid when its almost the cost of a decent set of WEBER's which I also have two good sets now.....

I don't know which way I will actually go at this point its still in though process stages ... But I am leaning towards IBT because of my Weber expediences ( I know means little with fuel injection).

Dale

[Eaallred]

My car cruises fine,

sorry, i do not find this to be a "scientific" approach. just because it "feels fine" does not mean that there is not improvment to be had. What does your torque curve look like? Is it as wide/flat as it "could be" without sacrificing top end? it is the same type of think that has some people still running points, because "it works fine".

Good thing I never claimed it to be "scientific" then.

I just counter-argue because ITB's are being led on to be believed as a 'bad' idea for light cruise scenario's. They are most definitly not.

I will elaborate though, ITB's are simple (other than linkage), and they work extremely well. Can you get better part throttle performance from a single TB setup with runners? sure/maybe, but you better be prepared to spend a LOT of time and money building and rebuilding intake systems until you get it right, because until you do get it right, you won't be out-performing a simple set of ITB's.

So in the meantime, anything i'm 'loosing' at part throttle with my ITB's, i'll just crack the throttle open a teensie bit more to overcome. If there is. I'm sure any difference is minimal.

I'm making the car street legal for next season, so i'll be getting more 'street time' with it to play more with part throttle tuning. It runs great at part throttle right now, and I really haven't done much tuning in that area at all. Up till now, I've only really focused on full throttle tuning.

[Redline Weber]

OK, then as mentioned above, make a new "air filter top" cover.

Install the fuel injector into it, then supply fuel to the top of the injector.

This can be easy with the Redline "threaded injector with top hat" style of injector.

This "Bell Mouth" injection is very common in F1 engines.

The fitted EMS should be able to inject fuel (low duty cycle) at 390 degrees ATDC for the Injection Instant, once per cycle.

Lance

[SUbuggy]

You missed the point completely- it's a race car.

So yes, 'it feels fine' is enough for Eric.

no i didn't miss the point at all. Actually, i think you "missed the boat" entirely on this thread. this thread is about what intake system "works best" (best torque curve) from 2-7k RPM. I still stand behind my belief that for this a plenum will work better than ITB. I am not saying it can't be done, we all know there are tons of people ou there doing it. thats not the point. there is always the good-better-best argument for any application.


if there is anyone here who has an ITB system and wants to convert to a plenum, i would be happy to dyno it for free and post the results.

[miniman82]

He said it works for him, what's not to understand? Who cares about part throttle HP anyway, the engine is throttled! If the engine feels smooth, pulls from a low RPM, and still has guts up top, then empirically he's getting exactly what he's after, end of story. You're not arguing with me, you're contesting what Eric has said. Maybe you should take this up with him?

[Eaallred]

I'm not going to argue that a single TB/plenum setup can make more power at lower rpms. Maybe it can, maybe it can. But I do know, that in order for it to make more power, you're going to invetst a lot of time and money into designing a setup that works best. I'm someone that doesn't have the time or money to do that, so ITB's were the perfect match for me.

Most of my "part throttle" driving is at the track. Going up the staging lanes, back on the return road, etc. So I fully admit that I don't have 'gobs' of part throttle action on my car.

But I can say that with my FK-89 cam and 48x38valve CE heads, my car will idle as low as 450rpm when cold (idles 800 warmed up) and drives around without hesitation and all that stuff. It "cruises" around the pits just fine at various rpms. It works VERY well. For me to design a single plenum intake that will still push my car into the 11.50's would take a lot more work and design. I really don't think this can be argued.

Overall, i'd love to go to a single TB. I even have a polished 65mm TB in my garage that I was going to use from the get-go. But the more I looked into it, the more I realized I was going to have to sink in a bunch of resources to get it 'right' that I didn't have avaliable to me. Time on the local chassis dyno (about 40 miles away) isn't cheap, something to this day I still can't afford. Seperate TB's fits the bill perfectly for someone in my situation.

But, on the bright side of things, i'm chipping away on this car to make it street legal so I can get more "part throttle drive time" in on this thing and do more tuning in that department. I just finished modifying the stock tank to sit in the stock location with the front end cut out of the car and straddling a 6" narrowed beam. With the pockets i've cut into it, I think i'm still at 10 gallon capacity, so I should be able to drive a decent amount on a full tank of E85. Switching back to an FK97 cam this year too, so we'll see how 'streetable' I can make it, and even more, see what kind of mileage I can get out of this thing with the E85. I'll be limited to cruising 50mph with my gearing, so it certainly won't be real spectacular. haha

[Humble]

Dale, am I correct in my guess that you have the blue buggy that runs down with UFO in Marina? If so are you coming to the awards/UFO club meeting? I'll be there and I should be able to answer any questions you have about megasquirt, efi, or TB choice. I was racing my bimmer this year but I've had both my supers out in the past, the yellow stocker, and the red and gray race super with all the porsche bits.

As for the throttle body for your buggy, knowing you I'd say dual CB 48mm or dual converted webers. The only down side to ITBs is very light throttle like cruise because the FI ecu sees a jump from say 70-80kpa to ambient pressure 98kpa (no filters in your case) within a few miliseconds with 1-3% throttle opening. In an autox buggy that really doesn't matter because I doubt you would be anywhere near light throttle during a run.

Will