Any one running this setup ?
eurotrashrabbit
I think that running ITB's on CIS would defeat the purpose a little. Having one throttle plate per cylinder would be good, but breathing through that air flow plate would not help things... Plus, ITB's usually require standalone engine management or something like megasquirt to manage the amount of fuel supply...
I doubt anyone will have gone through the trouble of hooking up ITB's to their stock Fuel distributor.
I doubt anyone will have gone through the trouble of hooking up ITB's to their stock Fuel distributor.
Re: (Jettaboy1884)
I've got to agree. That set-up would probably would tolerate a really big cam better then a normal CIS set-up but I doubt that would make it worth all the bother.
| Quote, originally posted by Jettaboy1884 » |
| I think that running ITB's on CIS would defeat the purpose a little. |
I've got to agree. That set-up would probably would tolerate a really big cam better then a normal CIS set-up but I doubt that would make it worth all the bother.
Re: ITB's on CIS (XKROMX)
I know a guy running this setup on his AutoX mk1 Jetta Coupe.
He made a custom air box that bolts up to the ITB's.
I believe the main reason he did it is because he's running a 306 race cam on a ABA and super high compression.
It's a pretty slick setup but all said and done, he isn't really much faster than my nicely modded 3A w/an Audi TB. His is a dedicated race car and completely gutted, lexan windows, etc. It weighs at least 500 lbs less than my piggish 2000lb Street Mod Rabbit.
The other problem he has is that he can't shut down the air enough to make it idle under 2500 RPM.
I know a guy running this setup on his AutoX mk1 Jetta Coupe.
He made a custom air box that bolts up to the ITB's.
I believe the main reason he did it is because he's running a 306 race cam on a ABA and super high compression.
It's a pretty slick setup but all said and done, he isn't really much faster than my nicely modded 3A w/an Audi TB. His is a dedicated race car and completely gutted, lexan windows, etc. It weighs at least 500 lbs less than my piggish 2000lb Street Mod Rabbit.
The other problem he has is that he can't shut down the air enough to make it idle under 2500 RPM.
Re: ITB's on CIS (eurotrashrabbit)
maybe he finds creativity amusing. or honesty. or curiosity.
personally i find it funny when people write lame posts with loads of smilies and are immediately shot down by the next poster who has 1st hand experience with the setup this guy was laughing at. but that's just me.
anyway, back on track: you're saying that the intake manifold and single throttle body setup is more restrictive than four TBs, i think. my understanding is that a fox intake mani and an A2 TB flow so well that the biggest restriction in the CIS system becomes the flow plate itself. if that's true ITBs woudl have no more gain than the Fox mod since they can both flow more air than the CIS box can flow. no?
maybe he finds creativity amusing. or honesty. or curiosity.
personally i find it funny when people write lame posts with loads of smilies and are immediately shot down by the next poster who has 1st hand experience with the setup this guy was laughing at. but that's just me.
anyway, back on track: you're saying that the intake manifold and single throttle body setup is more restrictive than four TBs, i think. my understanding is that a fox intake mani and an A2 TB flow so well that the biggest restriction in the CIS system becomes the flow plate itself. if that's true ITBs woudl have no more gain than the Fox mod since they can both flow more air than the CIS box can flow. no?
Re: ITB's on CIS (Crash-N-Burn)
Absolutely! It's been done, and probably with a certain level of sucess by others out there. Is it best? Who's to say. Is it stupid? Not to the guy who pulled it off with many hours of hard work and custom fabricating, and is very competitive with it.
If you're the type that thinks that the only mod is what everyone else is doing at the moment and everything else is stupid, the Mk4 furums are that way^^^^.
![Image]()
Absolutely! It's been done, and probably with a certain level of sucess by others out there. Is it best? Who's to say. Is it stupid? Not to the guy who pulled it off with many hours of hard work and custom fabricating, and is very competitive with it.
If you're the type that thinks that the only mod is what everyone else is doing at the moment and everything else is stupid, the Mk4 furums are that way^^^^.
Re: ITB's on CIS (Don D)
the closet I've seen was the "wretched excess" rabbit running dual throttle bodies on a modified 8v style intake..
Correct me if I'm wrong, but I belive old Hilborn style injection was mechanical, and iv'e seen those set up on a ITB type setup...actuall saw that setup for sale once, was used on a dasher that was built to run pike's peak...was Hugh's VW shop in Colorado springs about 12 years ago
![Image]()
the closet I've seen was the "wretched excess" rabbit running dual throttle bodies on a modified 8v style intake..
Correct me if I'm wrong, but I belive old Hilborn style injection was mechanical, and iv'e seen those set up on a ITB type setup...actuall saw that setup for sale once, was used on a dasher that was built to run pike's peak...was Hugh's VW shop in Colorado springs about 12 years ago
Re: ITB's on CIS (eurotrashrabbit)
I've always wondered about those old style mechanical systems, for instance, how'd they meter the air? Anybody got any good links? I'd like to learn more.
| Quote, originally posted by eurotrashrabbit » |
That would be another option is mechanical injector pump style fuel injection like old Porsche and Mercedes and Formula Vee
|
I've always wondered about those old style mechanical systems, for instance, how'd they meter the air? Anybody got any good links? I'd like to learn more.
Re: ITB's on CIS (ABA Scirocco)
I have worked on many of the older Benz's and they can be frustrating. Since people pay me to work on them it is not so bad but if I had to do it on my own then forget it.
The basic principle is that it will add more fuel with the opening of the throttle. There is linkage that attaches the throttle to the pump. This linkage has all the right angles since opening up the pump linkage will just allow more fuel to be pumped in. Linkage is critical and when it wears out then you're asking for trouble. There are usually high speed and low speed cams that can be adjusted [inside the pump]. From my understanding this adjusts a spring that will allow more tension to decrease the amount of fuel. There is a low speed [idle] correction screw as well. When you adjust the air screw for a higher idle you are just adding more air and not fuel. You have to add more fuel with the pump screw. When this happens the idle speed usually goes up and then you must decrease the air, which then effects you idle again. It goes on and on but when you have the right person working on it that understands it then it works pretty good [remember no cat converters or O2 sensors here]. There is an aux air valve that will allow for more fuel when cold [and air] that is located on the pump. As for fine tuning [such as a manifold pressure sent up on EFI systems] there is none. The fuel is dumped by how much the pump linkage is moved. Match that up with how much the throttle is moving and you're all good.
I am not good at explaining things and if someone shows up in my shop or house at $125/hr I could explain it more [It's not my shop and I do not set the shop charges] and yes I am only joking [not the shop charges].
| Quote, originally posted by ABA Scirocco » |
I've always wondered about those old style mechanical systems, for instance, how'd they meter the air? Anybody got any good links? I'd like to learn more. |
I have worked on many of the older Benz's and they can be frustrating. Since people pay me to work on them it is not so bad but if I had to do it on my own then forget it.
The basic principle is that it will add more fuel with the opening of the throttle. There is linkage that attaches the throttle to the pump. This linkage has all the right angles since opening up the pump linkage will just allow more fuel to be pumped in. Linkage is critical and when it wears out then you're asking for trouble. There are usually high speed and low speed cams that can be adjusted [inside the pump]. From my understanding this adjusts a spring that will allow more tension to decrease the amount of fuel. There is a low speed [idle] correction screw as well. When you adjust the air screw for a higher idle you are just adding more air and not fuel. You have to add more fuel with the pump screw. When this happens the idle speed usually goes up and then you must decrease the air, which then effects you idle again. It goes on and on but when you have the right person working on it that understands it then it works pretty good [remember no cat converters or O2 sensors here]. There is an aux air valve that will allow for more fuel when cold [and air] that is located on the pump. As for fine tuning [such as a manifold pressure sent up on EFI systems] there is none. The fuel is dumped by how much the pump linkage is moved. Match that up with how much the throttle is moving and you're all good.
I am not good at explaining things and if someone shows up in my shop or house at $125/hr I could explain it more [It's not my shop and I do not set the shop charges] and yes I am only joking [not the shop charges].
Re: ITB's on CIS (Butcher)
So you're saying that basically the fuel is metered strictly by throttle position and by the rpm the fuel pump is turning and then there are a few extra bits added for idling and warm-up.
FWIW, that sounds like a somewhat crude analog of the n-alpha fuel metering that's usually used on ITBs running efi. For those not familiar with the term n-alpha, that just means the the ecu meters the fuel based on just RPM, throttle position, air intake temperature and sometimes atmospheric pressure.
So you're saying that basically the fuel is metered strictly by throttle position and by the rpm the fuel pump is turning and then there are a few extra bits added for idling and warm-up.
FWIW, that sounds like a somewhat crude analog of the n-alpha fuel metering that's usually used on ITBs running efi. For those not familiar with the term n-alpha, that just means the the ecu meters the fuel based on just RPM, throttle position, air intake temperature and sometimes atmospheric pressure.
Re: ITB's on CIS (ABA Scirocco)
Yeah, this makes sense to me. When you run an ITB setup, you are doing it with a couple goals in mind: One throttle plate per cyl for better response. The other is to eliminate the stock airbox. Another is to have an engine management/fuel injection system that is more tunable and does not call for any type of restriction in the intake. Eg. a airflow plate, or a MAF (Digifant)
What I am interested in knowing, is what is the most restrictive part of the CIS intake? I would figure on A1's it is first the Throttle body, but at what point does the airflow plate become more restrictive than the tb?
After upgrading the TB, what is the next most restrictive part, the Airflow plate? At what point is the cylinder head itself the most restrictive part when compared to the other parts of the intake tract?
In my opinion, the best way of setting things up is to have all of the intake parts working at the peak performance of all the other parts. (with no one part being more restrictive than the other) At that point your intake is most efficient.
Does anyone know of a CIS compatible fuel distributor that has a bigger airflow plate???
| Quote, originally posted by ABA Scirocco » |
| So you're saying that basically the fuel is metered strictly by throttle position and by the rpm the fuel pump is turning and then there are a few extra bits added for idling and warm-up. FWIW, that sounds like a somewhat crude analog of the n-alpha fuel metering that's usually used on ITBs running efi. For those not familiar with the term n-alpha, that just means the the ecu meters the fuel based on just RPM, throttle position, air intake temperature and sometimes atmospheric pressure. |
Yeah, this makes sense to me. When you run an ITB setup, you are doing it with a couple goals in mind: One throttle plate per cyl for better response. The other is to eliminate the stock airbox. Another is to have an engine management/fuel injection system that is more tunable and does not call for any type of restriction in the intake. Eg. a airflow plate, or a MAF (Digifant)
What I am interested in knowing, is what is the most restrictive part of the CIS intake? I would figure on A1's it is first the Throttle body, but at what point does the airflow plate become more restrictive than the tb?
After upgrading the TB, what is the next most restrictive part, the Airflow plate? At what point is the cylinder head itself the most restrictive part when compared to the other parts of the intake tract?
In my opinion, the best way of setting things up is to have all of the intake parts working at the peak performance of all the other parts. (with no one part being more restrictive than the other) At that point your intake is most efficient.
Does anyone know of a CIS compatible fuel distributor that has a bigger airflow plate???
Re: ITB's on CIS (eurotrashrabbit)
Here are some pics from that "Wretched Excess" article:
http://www.evanscooling.com/articles/oct93ec.htm
![Image]()
![Image]()
"Although untested, twin throttle bodies do look impressive. Expensive modifications to improve airflow have yet to yield big gains."
I believe that the reason why they did not notice big gains from this setup is because they were running the stock airbox/fuel Distributor...
This just reinforces the idea that ITB's on a stock airbox/fuel Dist. will most likely not make big gains...
Read the article, it has some interesting information.
Here are some pics from that "Wretched Excess" article:
http://www.evanscooling.com/articles/oct93ec.htm
"Although untested, twin throttle bodies do look impressive. Expensive modifications to improve airflow have yet to yield big gains."
I believe that the reason why they did not notice big gains from this setup is because they were running the stock airbox/fuel Distributor...
This just reinforces the idea that ITB's on a stock airbox/fuel Dist. will most likely not make big gains...
Read the article, it has some interesting information.
Re: ITB's on CIS (salteatervw)
I would imagine they'd need to be adjusted for any major change in air density, and a big elevation change could certainly cause that.
| Quote, originally posted by salteatervw » |
| ive heard that too, especially if you wanna go up like 1000ft in elevation, i heard they get pretty bad in major elevation change |
I would imagine they'd need to be adjusted for any major change in air density, and a big elevation change could certainly cause that.
Re: ITB's on CIS (ABA Scirocco)
Yup that's about it. Remember back then emissions were not that big of a concern so if you are off by 1-3% CO no one was concerned.
| Quote, originally posted by ABA Scirocco » |
| So you're saying that basically the fuel is metered strictly by throttle position and by the rpm the fuel pump is turning and then there are a few extra bits added for idling and warm-up. . |
Yup that's about it. Remember back then emissions were not that big of a concern so if you are off by 1-3% CO no one was concerned.
Re: ITB's on CIS (Jettaboy1884)
I actually considered moving the battery to the trunk and running a dual fuel disty setup with 2 TB's. The idea is this: 2 fuel disty's, but block off 2 lines from each. So each disty only feeds 2 injectors. Each disty feeds a TB. It can't be much more difficult to tune than dual carbs. It's just a thought that maybe someone can go with. I have neither the $ nor the time to try it.
Thomas
| Quote, originally posted by Jettaboy1884 » |
| Here are some pics from that "Wretched Excess" article: http://www.evanscooling.com/articles/oct93ec.htm
"Although untested, twin throttle bodies do look impressive. Expensive modifications to improve airflow have yet to yield big gains." I believe that the reason why they did not notice big gains from this setup is because they were running the stock airbox/fuel Distributor... This just reinforces the idea that ITB's on a stock airbox/fuel Dist. will most likely not make big gains... Read the article, it has some interesting information. |
I actually considered moving the battery to the trunk and running a dual fuel disty setup with 2 TB's. The idea is this: 2 fuel disty's, but block off 2 lines from each. So each disty only feeds 2 injectors. Each disty feeds a TB. It can't be much more difficult to tune than dual carbs. It's just a thought that maybe someone can go with. I have neither the $ nor the time to try it.
Thomas
Re: ITB's on CIS (Jettaboy1884)
> When you run an ITB setup, you are doing it with a couple goals in mind: One throttle plate per cyl for better response. The other is to eliminate the stock airbox.
Exactly. I've heard from others that race VW's that one reason throttle bodies are better for that type of application is that they effectively eliminate the long / complex intake tract on a CIS car.
If you think about it, the air in a CIS system has to travel from under the air filter, up through the metering head and then up the tubing, past the throttle body, through the runners and finally into the head.
Figure two or three feet and a "column" of air that must react to throttle changes all along that stream.
The ITB systems I've seen (8V non-crossflow) have an air tract of about 10 inches or so. That said, I'm sure some would argue that the CIS system does an impressive job of responding to fueling changes and that the long "runners" of the intake manifold / tract actually help low end torque.
Presumably, the short / fast-reacting intake on an ITB car helps high in the rpm range and may slightly flatten out the bottom of the range. Depends on the application.
>>Another is to have an engine management/fuel injection system that is more tunable and does not call for any type of restriction in the intake. Eg. a airflow plate, or a MAF (Digifant)
True again. I'm presently planning an EFI swap (034) and one of my main motivations is ditching the restrictions / complexity of CIS while gaining the tunability and logging of a modern mgmt system.
Although CIS can be tuned to run rather well, I think that EFI can really zero in on exact fuel / spark inputs better than the factory setup. Others with EFI will chime in... I'm counting on better throttle response from eliminating the CIS setup.
For me, I plan to get the FSP car running again with a G60 intake (shorter, larger diameter runners, no CSV to block off and ports to block) and the Passat auto throttle body (best compromise I could come up with of off-the-shelf parts) and establish a baseline (I've got CIS dyno baselines from my car as well).
It'd be great to do ITB's, but as many have found out, the ones on the market are rather expensive and I don't have the means to adapt my own (motorcyle ITB's) at the moment.
>>... what is the most restrictive part of the CIS intake? I would figure on A1's it is first the Throttle body, but at what point does the airflow plate become more restrictive than the tb?
Without a flow bench and more data, I can't say for sure, but I do know some like PTong and others have made a lot of power keeping a stock style intake.
Port matching and porting go a long way (stock castings vary a great deal). I would agree with you that the stock CIS flapper is a restriction in that it might be slow to react and does in fact sit directly in the airstream.
There are many factors to making more power and the intake is only one piece of the puzzle. Factor in improvements in exhaust manifolds/ headers, compression ratio, cam profile, budget etc and you have a pretty complex formula.
>>Does anyone know of a CIS compatible fuel distributor that has a bigger airflow plate???
I thought I heard something about some early Porsche (924?) parts being slightly better... Perhaps in the actual shape of the cone in the fuel distributor, but I could be wrong.
Hope that helps...
> When you run an ITB setup, you are doing it with a couple goals in mind: One throttle plate per cyl for better response. The other is to eliminate the stock airbox.
Exactly. I've heard from others that race VW's that one reason throttle bodies are better for that type of application is that they effectively eliminate the long / complex intake tract on a CIS car.
If you think about it, the air in a CIS system has to travel from under the air filter, up through the metering head and then up the tubing, past the throttle body, through the runners and finally into the head.
Figure two or three feet and a "column" of air that must react to throttle changes all along that stream.
The ITB systems I've seen (8V non-crossflow) have an air tract of about 10 inches or so. That said, I'm sure some would argue that the CIS system does an impressive job of responding to fueling changes and that the long "runners" of the intake manifold / tract actually help low end torque.
Presumably, the short / fast-reacting intake on an ITB car helps high in the rpm range and may slightly flatten out the bottom of the range. Depends on the application.
>>Another is to have an engine management/fuel injection system that is more tunable and does not call for any type of restriction in the intake. Eg. a airflow plate, or a MAF (Digifant)
True again. I'm presently planning an EFI swap (034) and one of my main motivations is ditching the restrictions / complexity of CIS while gaining the tunability and logging of a modern mgmt system.
Although CIS can be tuned to run rather well, I think that EFI can really zero in on exact fuel / spark inputs better than the factory setup. Others with EFI will chime in... I'm counting on better throttle response from eliminating the CIS setup.
For me, I plan to get the FSP car running again with a G60 intake (shorter, larger diameter runners, no CSV to block off and ports to block) and the Passat auto throttle body (best compromise I could come up with of off-the-shelf parts) and establish a baseline (I've got CIS dyno baselines from my car as well).
It'd be great to do ITB's, but as many have found out, the ones on the market are rather expensive and I don't have the means to adapt my own (motorcyle ITB's) at the moment.
>>... what is the most restrictive part of the CIS intake? I would figure on A1's it is first the Throttle body, but at what point does the airflow plate become more restrictive than the tb?
Without a flow bench and more data, I can't say for sure, but I do know some like PTong and others have made a lot of power keeping a stock style intake.
Port matching and porting go a long way (stock castings vary a great deal). I would agree with you that the stock CIS flapper is a restriction in that it might be slow to react and does in fact sit directly in the airstream.
There are many factors to making more power and the intake is only one piece of the puzzle. Factor in improvements in exhaust manifolds/ headers, compression ratio, cam profile, budget etc and you have a pretty complex formula.
>>Does anyone know of a CIS compatible fuel distributor that has a bigger airflow plate???
I thought I heard something about some early Porsche (924?) parts being slightly better... Perhaps in the actual shape of the cone in the fuel distributor, but I could be wrong.
Hope that helps...
Re: ITB's on CIS (Thomas_covenant)
I like this idea. I think that with other performance mods this would work pretty well... The only negative thing is extra weight, but it's not much.
It would look pretty cool if you set it up so that one fuel dist. is on the Driver side, and the other is on the passenger side. It would look neat being balanced.
Veetesse: Your points are dead on. Thanks for the response. I will ask around about that porsche distributor...
| Quote, originally posted by Thomas_covenant » |
I actually considered moving the battery to the trunk and running a dual fuel disty setup with 2 TB's. The idea is this: 2 fuel disty's, but block off 2 lines from each. So each disty only feeds 2 injectors. Each disty feeds a TB. It can't be much more difficult to tune than dual carbs. It's just a thought that maybe someone can go with. I have neither the $ nor the time to try it. Thomas |
I like this idea. I think that with other performance mods this would work pretty well... The only negative thing is extra weight, but it's not much.
It would look pretty cool if you set it up so that one fuel dist. is on the Driver side, and the other is on the passenger side. It would look neat being balanced.
Veetesse: Your points are dead on. Thanks for the response. I will ask around about that porsche distributor...
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