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wickedmotorhead
11-07-2004, 08:34 PM
After seeing MSD's new velocity stack type mechanical fuel injection I have decided that I would like to do something similar with my Chevelles Rat. I saw kinsler had a nice EFI setup for the BBC. Does anyone know the pro's and con's of this system and how well it would work with my current setup? (see webpage for current engine specs). I am currently running a 1050 Dominator. I noticed also that hilborn had a cross ram mechanical type. I will be building a cold air forced induction system for whatever I choose and I thought the hilborn side intake runners would package best and would allow for a sweet custom cold air intake setup. I have no idea of what throttle size to run or what kind of horsepower these can accomodate. Basically any information anyone could give would be much appreciated. THANKS.

Fuelie Fan
11-08-2004, 10:14 AM
All I can tell you is the hilborn efi uses a "Carabine" ecu, which is not good for much more than a door stop. Throttle size should be pretty easy to determine for a given horsepower, their basic tech support should tell you. If not, you could always calc an estimate, you're an ME.

wickedmotorhead
11-09-2004, 09:06 PM
Damn! you caught me in my laziness. :banghead:

Good to know on the Hilborn types, I guess I'll stick with the Kinsler which can use the FAST setup. Basically I was wondering if anyone has had any experience with these and how they would rate them. I thought it would be a different approach on something a little different. Thanks.

camcojb
11-09-2004, 09:59 PM
I ran the Hilborn on a small block with a FAST ecu. Worked awesome. You can get the setup from them without their Carabine ecu which is almost worthless.
https://static1.pt-content.com/images/pt/2004/11/cobramotor-1.jpg

Jody

andrewb70
11-10-2004, 06:49 AM
THe new MSD setup will only fit small blocks.

Andrew

KendallF
11-10-2004, 08:15 AM
Damn! you caught me in my laziness. :banghead:

Good to know on the Hilborn types, I guess I'll stick with the Kinsler which can use the FAST setup. Basically I was wondering if anyone has had any experience with these and how they would rate them. I thought it would be a different approach on something a little different. Thanks.

If you want to do it relatively inexpensively, look for an old mech. FI intake and convert it. Then you can buy the FAST system or whatever; the GM sensors are dirt cheap. A friend of mine's going to do this for his 500+ ci Hemi in a 65 Belvedere. He bought an older stack style intake cheaply and I have it right now to machine and weld injector bungs and fuel rails. With 8 individual throttle butterflies that are something like 2.25" diameter each, it should make some big HP.

camcojb
11-10-2004, 09:05 AM
If you want to do it relatively inexpensively, look for an old mech. FI intake and convert it. Then you can buy the FAST system or whatever; the GM sensors are dirt cheap. A friend of mine's going to do this for his 500+ ci Hemi in a 65 Belvedere. He bought an older stack style intake cheaply and I have it right now to machine and weld injector bungs and fuel rails. With 8 individual throttle butterflies that are something like 2.25" diameter each, it should make some big HP.


Just realize one thing on these individual runner setups; they do not have a common plenum to "borrow" air from. You get what that individual butterfly will flow and that's it. On my 406 it had 2 3/16" butterflies. Total airflow about 2300 cfm or so. But only about 280-285 cfm per port, and my heads flowed 312 cfm. So although it made 480 rwhp with a 10:1 406 and some good heads, it was still airflow restricted.

Make sure you have a butterfly that will flow enough to keep up with your heads or you will cost yourself some power. A 2.25" blade on a 500 cid Hemi may not make as much power as it should.

Jody

Fuelie Fan
11-10-2004, 10:08 AM
You can't just blindly compare cfm numbers like that. THey are rated TOTALLY differently. Your heads, for example, were probably measured at 28" drop, where as carbs and throttle bodies are measured either at 1.5 or 3". Port flows are great for comparison between heads, but those numbers mean crapolla as far as how much air will move through your engine


Example: your 406.
Each cylinder = 406/8 = 50.75 in^3
Assume 6500 RPM peak hp
Assume 100% VE
airflow_per_cyl = (50.75 in^3/intake) * (1.0) * (6500 rev/min) * (1 intake/2 rev) * (1ft/12in)^3 = 95 cfm.

Unless you want to claim your engine has 300% VE???????

camcojb
11-10-2004, 10:13 AM
You can't just blindly compare cfm numbers like that. THey are rated TOTALLY differently. Your heads, for example, were probably measured at 28" drop, where as carbs and throttle bodies are measured either at 1.5 or 3". Port flows are great for comparison between heads, but those numbers mean crapolla as far as how much air will move through your engine


Example: your 406.
Each cylinder = 406/8 = 50.75 in^3
Assume 6500 RPM peak hp
Assume 100% VE
airflow_per_cyl = (50.75 in^3/intake) * (1.0) * (6500 rev/min) * (1 intake/2 rev) * (1ft/12in)^3 = 95 cfm.

Unless you want to claim your engine has 300% VE???????


How about comparing it like this? I had the heads ported and flowed by a local head porter. I then had the manifold and air doors flowed on the same flow bench by the same guy at the same pressure; they flowed almost 30 cfm less on the intake ports of my heads. Not huge, but just trying to make a point. You look at these setups and the total airflow and think they'll support unreal HP and that's not necessarily true. I would try to get a butterfly size that's not more restrictive than my heads, that's all I was pointing out.

Jody

Fuelie Fan
11-10-2004, 10:38 AM
I will, agree, however, that the lack of plenum does change throttle sizing. The intake is only open roughly a third of the time, hence the throttle body must be oversized so that it can provide higher peak flows, even though the average flow rate is much lower. THIS is why a seemingly huge amount of flow poetential on the induction may still be limiting things on an IR setup. Head design influences your VE in the calc above, it does NOT solely dictate the flow rate. Obviously changing engine displacement, cam timing, etc all affect the VE as well.

I am fully aware of the coincidence of the 300% ve and the 1/3 time for intake open, but it is only that, and they are rough numbers. You could use them perhaps as starting points, but you certainly cannot use them to make decisions on whether a 20-30 cfm difference is limiting your engine. If those heads were on a 383, and if the cam had 10 degrees fewer timing, everything would be totally different.

On a common plenum vehicle, it easy to determine if your throttles are limiting you: measure manifold pressure. On IR, it is much more difficult. You will see drastic fluctuations in pressure even on a properly set-up engine. For the enthusiast without the luxury of 4-6 bore sizes to experiment with, you have a couple options: link the ports with vacuum line and create a mini "plenum" and measure pressure there, or consult someone with a lot of experience like Jody or Kinsler or Hilborn.

Jody, I still have no doubt about the fact that you know how to build power, your record speaks for itself. As with all my posts, none of this is meant as a personal attack, I am just a stickler for techinicalities.

Fuelie Fan
11-10-2004, 10:38 AM
"techinicalities"

but obviously not spelling :)

camcojb
11-10-2004, 10:47 AM
No problem! This same engine made 20 rwhp MORE with a Super Victor efi manifold and 1000 cfm throttle body; it also made 30 rwtq LESS. That was with no changes, so it seems the IR was restricting it some, not a bunch. I'd gladly give up the 20 rwhp for the gain of 30 rwtq and the looks factor!

The guy I bought this setup from swapped from the 2 3/16" butterflies to 2 7/16"; he picked up almost 50 rwhp, but it was a pretty serious motor. No other changes (at that time). I also was involved with a 500 cid aluminum Shelby motor in a Cobra that made barely 400 rwhp with a large solid roller and fully ported heads. He was using the Imagine (I believe) individual throttle body setup. Looks were over the top, but he was not satisfied with the power. Swapped that setup for a large single plane converted manifold and 1000 cfm throttle body and picked it up to the 450-460 rwhp range as I remember; big difference in top end power, but lost some bottom end.

I just saw the 500 cid Hemi post and thought I'd throw out the importance of butterfly size on these systems. I think a 2.25" will be too small for peak power on that, but again it would matter how serious the engine really is.

Jody

Fuelie Fan
11-10-2004, 01:18 PM
Something I would add to that is what we are talking about and what you've seen is more than just "restriction". Changing the diameter and length of the throttle bodies and trumpets is directly changing the tuned peak of the system. It is possible that continuing to go bigger could also cost power. Luckily, on individual runner systems the natural frequency is pretty easy to determine.

I am continuing to verge off-topic, again tech support should be able to tell shane what would work for his setup.

OHCbird
11-10-2004, 11:15 PM
TWM makes TBs for many apps; Although not on their website, I do believe they have started making BBC setups similar to this (the unit pictured is an SBC). I helped build a retrofitted Lambo Miura w/ TWM TBs; they make a great product. Anyway ya slice it- get ready to spend!
https://static1.pt-content.com/images/noimg.gif

camcojb
11-11-2004, 09:21 AM
Something I would add to that is what we are talking about and what you've seen is more than just "restriction". Changing the diameter and length of the throttle bodies and trumpets is directly changing the tuned peak of the system. It is possible that continuing to go bigger could also cost power. Luckily, on individual runner systems the natural frequency is pretty easy to determine.

I am continuing to verge off-topic, again tech support should be able to tell shane what would work for his setup.


I agree. There is too big also. Just a lot of people look at the total airflow rating of an IR setup and try to compare it with a single plane/carb or throttle body setup and it's a completely different thing.

Jody

wickedmotorhead
11-11-2004, 07:50 PM
Wow that TWM system is pretty sweeeet! BUT expensive as hell. Thanks for the info.

wickedmotorhead
11-11-2004, 07:54 PM
Wow that TWM system is sweet! I dig the Carbon Fiber air horns. They are expensive though. Comparing to the BBF system the BBC chevy would be around 5G's! That's without the ECU system. WOW! Makes my carburator look a lot better. I just can't imagine seeing that much of an improvement other than dialing stuff in and efficiency and of course the cool factor!

Fuelie Fan
11-12-2004, 09:55 AM
Yeah, TWM's very pricy, yet Gary kind of has the attitude that you should be lucky he's even letting you buy it in the first place! He's a funny bloak to talk to though. I'm biased becuase I like to do everything on the cheap, but I certainly wouldn't pay that much.

KendallF
11-12-2004, 09:24 PM
Camco and FuelieFan, I'm glad you guys commented..made me think. Also made me curious and I went and actually measured the bores on the intake destined for the Hemi. The motor is a crate Hemi (528"? I think so..I've only seen the motor once). The bores are actually 2.40" diameter; they should do well for a street motor that sees the track occasionally. The plan is to tie in the old mech nozzle bores to a small plenum located in between the stacks for a common vac signal for IAC. It will be running DFI Gen 7.

camcojb
11-12-2004, 09:34 PM
Camco and FuelieFan, I'm glad you guys commented..made me think. Also made me curious and I went and actually measured the bores on the intake destined for the Hemi. The motor is a crate Hemi (528"? I think so..I've only seen the motor once). The bores are actually 2.40" diameter; they should do well for a street motor that sees the track occasionally. The plan is to tie in the old mech nozzle bores to a small plenum located in between the stacks for a common vac signal for IAC. It will be running DFI Gen 7.


Fine for a street deal; too small for max power in my opinion. What are you going to do for a map sensor line?

Jody

David Pozzi
11-13-2004, 01:17 AM
Here is a runner dia calculator. It is a motorcycle page but give it a try: http://www.rbracing-rsr.com/runnertorquecalc.html

Fuelie Fan
11-13-2004, 12:09 PM
That's an odd calculator, it doesn't ask anything about length, which is confusing to me. since it is a motorcycle page, they are probably able to assume that the carb is very near the port, and can safely assume a runner length = port length + carb length and be right for about 90% of the bikes out there. I can't remember off-hand what the port length was on the R6 that I built an intake for, but I think it was around 4-5". Figure a side-draft MC carb adds another 3-4" for a total assumed length of 7-9". Your hemi setup is most likely going to have a longer intake tract, probably at least 12"-16" I would think, which will shift the peak lower (that calculator gave a TORQUE peak of 6000 rpm for the hemi, I would think that's a bit high )

ItsA68
11-14-2004, 09:06 AM
I am building a 400 cid motor for my 68 Camaro, and am hoping to get the TWM unit, along with a DFI v7 ECU. TWM only offers the system in 48 or 50 mm throttle bodies. The 50mm units flow 410CFM per barrel at 1.5in/hg . Do you guys think thats big enough for 550-600 hp, and max 6500 rpms? They use the 55 and 58 mm units on the big fords. I think it would easy enough to use the regular chevy manifold, and just swap out the throttle bodies for the larger ones, and then blend out the difference in the manifold. Would it be worth it? If the throttle bodies were too big, what would happen?

~~fred

camcojb
11-14-2004, 09:25 AM
My guess is it is too small. I think they'd support 500 HP but would be airflow challenged at 550-600. I'd want to know the flow at the same 28" that the heads are flowed at. I used 2 3/16" throttle blades on the Hilborn and made 480 rwhp which could be app. 575-600 HP at the crank. But they're quite a bit larger than 50mm. The 55mm size is close to the 2 3/16" I used and should be close.

That 500 cid Ford gained 50-60 rwhp by swapping away from the largest throttle body from them and using a single plane intake and 4 barrel throttle body. No comparison for looks though.

ItsA68
11-14-2004, 09:31 PM
could you provide any more specific info about your motor with the hilborn system in the cobra? It looks like you have already built about what I am working toward. What heads did you use? And what cam? Lift? duration? If you did it over, what would you change? On the TWM setup, they have a system that links all the runners together for a place to put the MAP sensor. What do you suppose they do about the manifold air temp sensor? What about IAC? I'm thinking that you can't have it....would it make a difference? I understand that you can run a very lumpy cam with an IR manifold, and still get a decent idle, what do you think?

camcojb
11-14-2004, 10:01 PM
You can run IAC but you'd need to add an additional line to each throttle body, separate of the map sensor line. It is nice to have and I recommend it.

You could run the air temp sensor in the airbox/air filter somewhere, or in one of the inlet tubes.

406 recipe:
406 2 bolt w/ARP studs and partially filled block
Eagle crank and rods, Ross pistons @ "0" deck (10:1 compression), Iron Eagle 230 heads fully ported, solid roller .625 lift and 264 @ .050 on a 110 lsa, 1.6 roller rockers, and that Hilborn setup controlled by a FAST ecu. The cam seems fairly large but the IR setup really tames a cam as you said. You could let the clutch out in first gear without touching the throttle and it would just putt along, no jumping or jerking.

Jody

Fuelie Fan
11-15-2004, 10:36 AM
Are you sure they don't mean per throttle body? I calculate a maximum of 293 cfm for a 50mm throttle body with a 8mm (5/16") throttle shaft at 1.5 inHg depression. Certainly there would have to be losses on top of that. Besides, if it were capable of 410cfm per bore, it would suggest that you would have excessive flow potential, not a possible restriction as jody suggests. Seat of the pants, I would tend to side with Jody that they are too small, simply becuase you are talking big block power levels.

As a side note, again I don't think getting a detailed flow test at 28 inH2O is worth your time, becuase it won't necessarily tell you where the restriction is in your engine. Besides, on something like a throttle body, you can probably asume Cd is going to be relatively constant from 20 to 28 inH2O (20 inH2O = 1.5 inHg), and simply use the predictive equations. In this case, multiply flow at 20 inH2O by 1.16 to get flow at 28 inH2O (notice it's NOT a linear function of pressure drop, a 40% increase in delta P only nets a 16% increase in flow). It should certainly get you that "ballpark" feel for whether they are a flow restriction or not. Since the throttle blades aren't seeing the same pressure profile as a port (it gets damped by the air volume before it and, depending on whether you run a stub like TWM's carbon pieces, could be entirely different altogether) I again express the opinion that you cannot directly compare flow rates of different parts within the minutia of a couple cfm.

ItsA68
11-15-2004, 01:04 PM
I'm only repeating what I was told via e-mail from the folks at TWM. to quote "All our flow measurements are "per barrel at 20.4 inches"" Their responses are very short, and they don't seem interested in elaborating on anything with their answers. I have not called them on the phone to ask a bunch of questions, yet, as I don't have the $$ and am not ready to purchase. Companies like this I'm sure get inundated with folks that have a lot of questions, and never buy anything. From their standpoint, I understand that they don't want to waste time on answering questions that probably won't lead to a sale. One would think that they would spend more time building a better web site that answered all of your questions. (the 410 CFM number isn't on their web site anywhere that I could find, I had to ask via e-mail) I would like to see a graph that shows recommended throttle bore size against RPM potential, and cylinder size. The Dellorto manual I have, has such a chart for picking carbs. I really think 50mm is too small also, and plan to pursure the setup with 55 or 58 mm throttle bodies. I am only worrying that the manifold will have enough material to increase the port size, and that it won't be a restriction itself. Is there any way to determine from the runner length, where in the power band the manifold would prefer to see max VE? It seems like it would be really important to match the cam with the manifold to make the best of the system. These are questions I will be asking of TWM when I am ready to buy. I hope that they can provide good answers.

~~fred

Fuelie Fan
11-15-2004, 02:48 PM
You are absolutely correct, you want your intake design to be part of the entire package: Cam size, head size, exhaust size, etc. This is why you don't run a huge single plane intake with short, mammoth diameter ports on mild low-rpm engine, for example. It'll be a real stinker.

there are numerous sources for determining proper runner length vs desired peak rpm. Grape ape racing has one on thier webpage, for example (it even takes into account cam timing, which does effect things). Another simple one (it ignores cam timing, but again we're looking for ballpark) is

N = (15*a/PI) * sqrt(Fp/(Lp*Vc))

Where N = engine speed, rev/min
a = speed of sound, 1100 ft/sec for air
PI = 3.14159
Fp = pipe cross-sectional area
Lp = pipe length
Vc = cylinder mean volume = half cylinder swept volume plus clearance volume

Rearranged to find Lp from desired rpm:

Lp = 225*Fp*a^2/(Vc*N^2*PI^2) *144 (the 144 is a unit conversion)

for your 400 (4.125" bore, 3.75" stroke), assume a 55mm (2.165") average port diameter
Vc = 25 in^3
N= 4500 rpm (peak torque, not peak hp)
Fp = 3.68 in^2

Lp = 225*3.68*1100^2*144/(25*4500^2*3.14159^2)

Lp = 28" I know, pretty stinkin long. BUT, you can cut that in half to get the second resonance. Therefore, you'd want a 14" induction tract. Be sure to include the length of your head port in this, though.