I submit that if the manifold is made for either/or, then there are likely significant gains left on the table for FI. No matter who made it. I'm betting that Accel made only one so they could sell manifolds to both carb and FI people without having to go through the expense of designing and manufacturing two separate pieces.
...You know, I'd be curious how Shad's Fastback did on the dyno with a pair of 48s on it... Almost makes me wish I had a spare pair of 48s (plus linkage, etc.) and a coupon for an hour of dyno time to send to him.
--DD
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1974 VW-Porsche 914 2.0 (Type IV powered!)
Pelican Parts' 914 Tech Geek http://www.pelicanparts.com
Why not carbs?
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Ghost Rider
- Posts: 227
- Joined: Sat Apr 06, 2002 12:01 am
Why not carbs?
true, some HP for FI may have been left on the table, but I'll bet the Carb had some minor HP that could have been gained too, from a different Manifold, different carb... etc... and yes if you tweaked bothto the max, FI probably would have slightly higher Dyno numbers, but I don't think the gap in numbers would have justified putting $5000+ into over the carbs... even a 10-12hp gain (realistic gap, I don't think it would be more than 20) on an engine that already produces 425+HP!! is worth 5000! let's face it, a big block Chevy will NEVER get GOOD gas milage... when you are talking about 14mpg(FI) vs. 12mpg(Carb) to me I would never give up carbs for 10hp and 2-4mpg! esspecially at $5000! now, if the car already had the FI(that works) ... that's a different story.. I'll take Carbs that work over FI that doesn't!
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MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
Why not carbs?
In short:
If the engine is 100% bone stock, leave it FI, if you have mods, swap to carbs....thats just me.
If the engine is 100% bone stock, leave it FI, if you have mods, swap to carbs....thats just me.
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ray greenwood
- Posts: 1941
- Joined: Thu Jul 19, 2001 12:01 am
Why not carbs?
There is no such thing as an either or manifold for FI and carbs. What makes a carb manifold work is not what makes a FI manifold work. If we are saying that the manifold is mid grade enough to run "decent" with either set-up...then there is no point in running injection at all....as there has been no specific tuning done and youwould have no idea if everything is optimal.
JAKE RABY...just a note. Although I have "0" experience fitting CIS to type 4, I thought I would drop a few warnings about some of the pitfalls of CIS in general..since I work on a lot of it. The posts I have read from the handful of people that do use it...point to some potential errors in thought. Many see CIS as much simpler than EFI. It is not. It is actually more complex in "character" and operation...but simpler in ececution. Let me give you an example of the moment. I spent till 2:00 a.m. changing the fuel pump on the SAAB...and rebalancing the fuel system pressures (yes my type 4 is still down). A variance of 2.5 PSI was the differnce between proper starting and max HP...and the exact opposite. Many state that their ystems run great. I sayu as compared to what? There is no "spec" for what a given system was optimized for,and should therefore have for a baseline output. The point of this being....do not shorten the system parameters by skipping parts, because the engine seems to run well without them. I know you won't...but for example, the control pressure regulator will have to be modified...unless you find one putting out the exact amount of pressurefor you application. If not, the airflow plate will not counterbalance properly. Be very exact on main fuel line pressures...and the volume to maintain them. As I noted...as little as 2.5 PSI..while being within the variance range of a stock injector, will cause the control pressure to give poor counter balance to the metering plate. This means flat spots and lean spots. The often overlooked part is the actual counterweight block on the back of the pivot arm. This can be moved...by a crafty person...farther or closer from the center of gravity...to adjust for inconsistancies/variances in control pressure. A whole 'nother dimension in tuning. Also, each injector must be balanced within 2 psi of opening pressure. Its feed can be balanced also if you have a distributor with the ajdustable ports. Lastly...do not snub the lambda version. It is the best. In all Lambda based systems...the frequency valve injector can be swapped/modified...again a whole'nother level of tuning. Each pulse from it modifys the control pressure for both proper acceleration and idle...based on 02 sensor flucuations. Which 02 sensor you use...is a whole 'nother level of tuning to choose from as well. The nifty thing is...that most lambda boxes have a two wire jack...that reads direct pulse relation on your trusty meter...to tell you when the pulse relation versus 02 sensor readout...is either rich...lean or factory baseline. Its readout is adjusted with the hex key from the fulrum plate. I love CIS...more power too ya. I have the actual metal backed factory manuals from SAAB...that give the very best in detail tuning references for CIS I have ever seen. If you would like a copy...let me know. Ray
JAKE RABY...just a note. Although I have "0" experience fitting CIS to type 4, I thought I would drop a few warnings about some of the pitfalls of CIS in general..since I work on a lot of it. The posts I have read from the handful of people that do use it...point to some potential errors in thought. Many see CIS as much simpler than EFI. It is not. It is actually more complex in "character" and operation...but simpler in ececution. Let me give you an example of the moment. I spent till 2:00 a.m. changing the fuel pump on the SAAB...and rebalancing the fuel system pressures (yes my type 4 is still down). A variance of 2.5 PSI was the differnce between proper starting and max HP...and the exact opposite. Many state that their ystems run great. I sayu as compared to what? There is no "spec" for what a given system was optimized for,and should therefore have for a baseline output. The point of this being....do not shorten the system parameters by skipping parts, because the engine seems to run well without them. I know you won't...but for example, the control pressure regulator will have to be modified...unless you find one putting out the exact amount of pressurefor you application. If not, the airflow plate will not counterbalance properly. Be very exact on main fuel line pressures...and the volume to maintain them. As I noted...as little as 2.5 PSI..while being within the variance range of a stock injector, will cause the control pressure to give poor counter balance to the metering plate. This means flat spots and lean spots. The often overlooked part is the actual counterweight block on the back of the pivot arm. This can be moved...by a crafty person...farther or closer from the center of gravity...to adjust for inconsistancies/variances in control pressure. A whole 'nother dimension in tuning. Also, each injector must be balanced within 2 psi of opening pressure. Its feed can be balanced also if you have a distributor with the ajdustable ports. Lastly...do not snub the lambda version. It is the best. In all Lambda based systems...the frequency valve injector can be swapped/modified...again a whole'nother level of tuning. Each pulse from it modifys the control pressure for both proper acceleration and idle...based on 02 sensor flucuations. Which 02 sensor you use...is a whole 'nother level of tuning to choose from as well. The nifty thing is...that most lambda boxes have a two wire jack...that reads direct pulse relation on your trusty meter...to tell you when the pulse relation versus 02 sensor readout...is either rich...lean or factory baseline. Its readout is adjusted with the hex key from the fulrum plate. I love CIS...more power too ya. I have the actual metal backed factory manuals from SAAB...that give the very best in detail tuning references for CIS I have ever seen. If you would like a copy...let me know. Ray
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MASSIVE TYPE IV
- Posts: 20132
- Joined: Fri Jul 07, 2000 12:01 am
Why not carbs?
I fully understand the theory and operation of CIS, thats why I used it.
I have 3 test engines with it right now and one more going on the dyno next week. You will notice I have stated TEST alot, thats because until I prove that I cannot break it, it don't get sold on my engines. So far a best of 31 MPG in a stroker TIV in my 74 bus, which averages 24-27 MPG loaded with 3,000 pounds of engines, crossing the smokey mountains in 90 degree heat passing cars all the way, I used 3rd gear once.
On my dyno the CIS was tuned to within 3HP of a pair of 44 Weber carbs, made over 70 lb/ft of torque at 500 RPM, which was equal to the webers at 2,000 RPM....
My chief engine builder has 19 years of CIS experience everything from Rabbits to Mercedes, even Pinzgauer Swiss military vehicles used it..
I have 3 test engines with it right now and one more going on the dyno next week. You will notice I have stated TEST alot, thats because until I prove that I cannot break it, it don't get sold on my engines. So far a best of 31 MPG in a stroker TIV in my 74 bus, which averages 24-27 MPG loaded with 3,000 pounds of engines, crossing the smokey mountains in 90 degree heat passing cars all the way, I used 3rd gear once.
On my dyno the CIS was tuned to within 3HP of a pair of 44 Weber carbs, made over 70 lb/ft of torque at 500 RPM, which was equal to the webers at 2,000 RPM....
My chief engine builder has 19 years of CIS experience everything from Rabbits to Mercedes, even Pinzgauer Swiss military vehicles used it..
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ray greenwood
- Posts: 1941
- Joined: Thu Jul 19, 2001 12:01 am
Why not carbs?
Very cool! Sorry I havn't had much time to keep up with your tests lately. Thats excellent results especially hauling 3000 lbs of sheet metal. Just didn't know if you had everything you needed. I have been watching what a lot of other people are trying with CIS. Gonna be a lot of mixed results. CIS is actually one of the most elegant systems, I think. I am happy your attention has turned to it. Ray