If anyone wants to design a manifold from scratch they might find this software useful. I've used similar s/w several times before, but never for a VW engine.
Be warned though, it gets pretty involved.
http://esp.stanford.edu/line.html
Throtle Bodies/ Manifolds where to get?
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Steve C
- Posts: 1143
- Joined: Sun May 14, 2000 12:01 am
Throtle Bodies/ Manifolds where to get?
Hi Sharkey
My Autronic SMC runs the TPS switch only as a limp home device. Let us know if find any diffence using the Map sensor.
Regards Steve C
My Autronic SMC runs the TPS switch only as a limp home device. Let us know if find any diffence using the Map sensor.
Regards Steve C
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Sharkey
- Posts: 966
- Joined: Sat Jul 22, 2000 12:01 am
Throtle Bodies/ Manifolds where to get?
Will do, Steve.
All dual dual set-ups have suffered from awkward off-idle performance, from small Dell 34s to honkin' huge 48 IDAs. For Chr*st sake, the largest aftermarket throttlebody you can buy for a 5.0 Mustang is 75mm, which translates into less cross-sectional area than a pair of dual 40mm throttlebodies or carbs (and 5.0 litres vs approximately half that in a huge ACVW engine). Why do we insist on running such huge throttlebodies or carbs when the bigblock V8 guys seem to be able to produce 400+ HP easily with a single 4-bbl?
What this translates to in my particular case is a LOT of increased airflow with only a teeny tiny opening of the throttle. I'm positive that the TPS records very little resistance change when this happens, and the computer only enriches the mixture a little. Sure, the base fuel pulse width will fatten up when the MAP sensor detects the drop in vacuum, but not until after the instance of acceleration enrichment.
Sigh. I kinda wanted to use my TPS to determine acceleration enrichment. After all, I paid for the damn thing. Now it looks like it will be a secondary sensor, good only for determining WOT (for clearing engine floods) or closed throttle (to cut off fuel while coasting). Oh yeah, I suppose I could still use it to operate a NOS switch someday down the road
All dual dual set-ups have suffered from awkward off-idle performance, from small Dell 34s to honkin' huge 48 IDAs. For Chr*st sake, the largest aftermarket throttlebody you can buy for a 5.0 Mustang is 75mm, which translates into less cross-sectional area than a pair of dual 40mm throttlebodies or carbs (and 5.0 litres vs approximately half that in a huge ACVW engine). Why do we insist on running such huge throttlebodies or carbs when the bigblock V8 guys seem to be able to produce 400+ HP easily with a single 4-bbl?
What this translates to in my particular case is a LOT of increased airflow with only a teeny tiny opening of the throttle. I'm positive that the TPS records very little resistance change when this happens, and the computer only enriches the mixture a little. Sure, the base fuel pulse width will fatten up when the MAP sensor detects the drop in vacuum, but not until after the instance of acceleration enrichment.
Sigh. I kinda wanted to use my TPS to determine acceleration enrichment. After all, I paid for the damn thing. Now it looks like it will be a secondary sensor, good only for determining WOT (for clearing engine floods) or closed throttle (to cut off fuel while coasting). Oh yeah, I suppose I could still use it to operate a NOS switch someday down the road
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turbo6bar
- Posts: 601
- Joined: Mon Dec 18, 2000 12:01 am
Throtle Bodies/ Manifolds where to get?
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Sharkey:
<B>
Why do we insist on running such huge throttlebodies or carbs when the bigblock V8 guys seem to be able to produce 400+ HP easily with a single 4-bbl?
</B><HR></BLOCKQUOTE>
Sharkey, can't compare inpedependent runner throttle bodies to single throttle bodies. Independent runner throttle plates are only under vacuum for a short amount of time, ie. when the intake valve is open, whereas a single throttle body is always under vacuum. Therefore, you need relatively large dual throttle bodies to allow air to rush into the cylinder.
Regarding your off-idle stumble, have you had the chance to tune your fuel and ignition map wel?. In the manual, they state you need to have a well prepared engine map, and THEN you adjust the accel. enrichment rate and delay. Just a thought. The TPS outputs roughly 0-5V from the analog potentiometer. It should give you pretty good resolution. To check, you should run an ohmeter across 2 contacts and see if your resistance changes for a small throttle change. I have a spare TPS laying around and can run some checks. Let me know.
Jay
<B>
Why do we insist on running such huge throttlebodies or carbs when the bigblock V8 guys seem to be able to produce 400+ HP easily with a single 4-bbl?
</B><HR></BLOCKQUOTE>
Sharkey, can't compare inpedependent runner throttle bodies to single throttle bodies. Independent runner throttle plates are only under vacuum for a short amount of time, ie. when the intake valve is open, whereas a single throttle body is always under vacuum. Therefore, you need relatively large dual throttle bodies to allow air to rush into the cylinder.
Regarding your off-idle stumble, have you had the chance to tune your fuel and ignition map wel?. In the manual, they state you need to have a well prepared engine map, and THEN you adjust the accel. enrichment rate and delay. Just a thought. The TPS outputs roughly 0-5V from the analog potentiometer. It should give you pretty good resolution. To check, you should run an ohmeter across 2 contacts and see if your resistance changes for a small throttle change. I have a spare TPS laying around and can run some checks. Let me know.
Jay
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Tom Notch
- Moderator
- Posts: 3332
- Joined: Mon Apr 10, 2000 12:01 am
Throtle Bodies/ Manifolds where to get?
I tend to disagree. My set up is so smooth even with the Web 86c cam its almost unreal. The only time I have had any kind of tip-in trouble is when the accel. maps were TOO rich! So I pulled them back until it sneezed then added just a bit, now just ultra smooth.
Those same Vee-ate engines when fitted with port injection and an equivelent TB to the carb usually pick up more horsies due to the evening out of the mixture due to poor runner length matches and associated flow mis-match. Plus our heads flow WAY better than their stuff.
If you start looking at hp per cubic inch, a 400 hp big block is like a 1776 putting out85 HP. or a 2161 putting out 100 hp. We got them beat bad. A 500 c.i. BB would have to put out 700-800 hp to have the same power to C.I. ratio. A 350 C.I. would have to put out 400+ also. And how much would either cost?
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Sharkey:
<B>Will do, Steve.
All dual dual set-ups have suffered from awkward off-idle performance, from small Dell 34s to honkin' huge 48 IDAs. For Chr*st sake, the largest aftermarket</B> throttlebody you can buy for a 5.0 Mustang is 75mm, which translates into less cross-sectional area than a pair of dual 40mm throttlebodies or carbs (and 5.0 litres vs approximately half that in a huge ACVW engine). Why do we insist on running such huge throttlebodies or carbs when the bigblock V8 guys seem to be able to produce 400+ HP easily with a single 4-bbl?<HR></BLOCKQUOTE>
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Tom Notch
Tom's Old VW Home
[This message has been edited by Tom Notch (edited 04-06-2001).]
Those same Vee-ate engines when fitted with port injection and an equivelent TB to the carb usually pick up more horsies due to the evening out of the mixture due to poor runner length matches and associated flow mis-match. Plus our heads flow WAY better than their stuff.
If you start looking at hp per cubic inch, a 400 hp big block is like a 1776 putting out85 HP. or a 2161 putting out 100 hp. We got them beat bad. A 500 c.i. BB would have to put out 700-800 hp to have the same power to C.I. ratio. A 350 C.I. would have to put out 400+ also. And how much would either cost?
<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Sharkey:
<B>Will do, Steve.
All dual dual set-ups have suffered from awkward off-idle performance, from small Dell 34s to honkin' huge 48 IDAs. For Chr*st sake, the largest aftermarket</B> throttlebody you can buy for a 5.0 Mustang is 75mm, which translates into less cross-sectional area than a pair of dual 40mm throttlebodies or carbs (and 5.0 litres vs approximately half that in a huge ACVW engine). Why do we insist on running such huge throttlebodies or carbs when the bigblock V8 guys seem to be able to produce 400+ HP easily with a single 4-bbl?<HR></BLOCKQUOTE>
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Tom Notch
Tom's Old VW Home
[This message has been edited by Tom Notch (edited 04-06-2001).]
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Dave_Darling
- Posts: 2534
- Joined: Thu Apr 27, 2000 12:01 am
Throtle Bodies/ Manifolds where to get?
Don't forget that high HP/cc numbers are easier to make in smaller engines. Ask any motorcycle builder. 
One of the amazing things about the Ferrari 355 motor when it came out a few years back was that it actually got ~100 HP/liter out of 3.5 liters! Motorcycles had been doing that for years, and Hondas had been doing that for a while with 1.6-1.8 liter motors.
--DD
One of the amazing things about the Ferrari 355 motor when it came out a few years back was that it actually got ~100 HP/liter out of 3.5 liters! Motorcycles had been doing that for years, and Hondas had been doing that for a while with 1.6-1.8 liter motors.
--DD
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Chris_914
- Posts: 250
- Joined: Fri Mar 16, 2001 12:01 am
Throtle Bodies/ Manifolds where to get?
My friend's two cylinder two stroke 650cc jetski put out 50 something HP but somehow I don't think it would power a bug, nor do I see a 300 HP bug pulling my boat to the lake. In a strong well rounded gasoline four stroke the HP and torque should be somewhat close to each other. While on the other end of the scale, lots torque over HP creates the massive pulling power of the small displacement diesels we have all come to share the road with.
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Chris
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Chris