Discussion
OK...loving the GTR, particularly like the sledgehammer delivery and howl of the supercharger 
. However would like to overcome some carb limitations....fuel use, lumpy low speed running, bit tempremental under hard braking etc. I know all these can be overcome with careful set up and attention to the carb.....but thinking of moving to Efi. The question is which one?
Throttle Body Injection or Multipoint with seperate throttle body......FAST, Holley or other.....
On the face of it I am thinking of using a 4 barrel TBI system as a direct replacement to holley carb....seems easier, especially as the supercharger has specific manifold so would need modifying for MPI.
Looking for some opinions and experiences to help me in the right direction particularly anyone who has got the before and after experience ....or anyone done this with a supercharged SBC... Ease of set up, performance etc.....all input gratefully recieved.
Stu
. However would like to overcome some carb limitations....fuel use, lumpy low speed running, bit tempremental under hard braking etc. I know all these can be overcome with careful set up and attention to the carb.....but thinking of moving to Efi. The question is which one?Throttle Body Injection or Multipoint with seperate throttle body......FAST, Holley or other.....
On the face of it I am thinking of using a 4 barrel TBI system as a direct replacement to holley carb....seems easier, especially as the supercharger has specific manifold so would need modifying for MPI.
Looking for some opinions and experiences to help me in the right direction particularly anyone who has got the before and after experience ....or anyone done this with a supercharged SBC... Ease of set up, performance etc.....all input gratefully recieved.
Stu
[quote=Mr Pid]OK...loving the GTR, particularly like the sledgehammer delivery and howl of the supercharger . However would like to overcome some carb limitations....fuel use, lumpy low speed running, bit tempremental under hard braking etc. I know all these can be overcome with careful set up and attention to the carb.....but thinking of moving to Efi. The question is which one?
Throttle Body Injection or Multipoint with seperate throttle body......FAST, Holley or other.....
On the face of it I am thinking of using a 4 barrel TBI system as a direct replacement to holley carb....seems easier, especially as the supercharger has specific manifold so would need modifying for MPI.
Looking for some opinions and experiences to help me in the right direction particularly anyone who has got the before and after experience ....or anyone done this with a supercharged SBC... Ease of set up, performance etc.....all input gratefully recieved.
Hi
Youve done a lovely job bringing that car back from the dead!!!
Please speak to Can Am Dave he has done it all with a supercharged EFI SBC. To be honest im not sure you will see a lot of benefit from fitting a EFI system to your motor, the type of blower you have fitted is killing your ecomomy and for the investment required i dont think the small improvement you will see is worth that investment. Imo i would maximise the setup you have and continue to enjoy the car.
The stalling can be fixed along with the other issues with the carb.
Ive fitted a EFI system to a SBC and i dont think it was worth the effort and investment.
. However would like to overcome some carb limitations....fuel use, lumpy low speed running, bit tempremental under hard braking etc. I know all these can be overcome with careful set up and attention to the carb.....but thinking of moving to Efi. The question is which one?Throttle Body Injection or Multipoint with seperate throttle body......FAST, Holley or other.....
On the face of it I am thinking of using a 4 barrel TBI system as a direct replacement to holley carb....seems easier, especially as the supercharger has specific manifold so would need modifying for MPI.
Looking for some opinions and experiences to help me in the right direction particularly anyone who has got the before and after experience ....or anyone done this with a supercharged SBC... Ease of set up, performance etc.....all input gratefully recieved.
Hi
Youve done a lovely job bringing that car back from the dead!!!
Please speak to Can Am Dave he has done it all with a supercharged EFI SBC. To be honest im not sure you will see a lot of benefit from fitting a EFI system to your motor, the type of blower you have fitted is killing your ecomomy and for the investment required i dont think the small improvement you will see is worth that investment. Imo i would maximise the setup you have and continue to enjoy the car.
The stalling can be fixed along with the other issues with the carb.
Ive fitted a EFI system to a SBC and i dont think it was worth the effort and investment.
My EFI is the best thing I could ever have done to a SBC. I guess it all depends on how badly set up your carb is and how much time money and effort you want to put in to get it right. Trouble is my ecu although very simple in some ways but brilliant in others cannot work with boosted engines.
My EFI is the best thing I could ever have done to a SBC. I guess it all depends on how badly set up your carb is and how much time money and effort you want to put in to get it right. Trouble is my ecu although very simple in some ways but brilliant in others cannot work with boosted engines.
Interesting, and quite different experiences.
I checked a bit deeper into the FAST EZ EFI system and also concluded it was not meant for any Turbo/blower applications. Seems the way it self calibrates makes an assumption that it is n/a.
As for fuel economy....I dont expect much advantage...but I do know mine is currently running quite rich throughout, so probably would gain some with either better carb set up or EFi. The main reason for considering EFi would be road manners at low (ish) revs.
Intend to keep an open mind for the moment so any further views would be welcome.
.......Meanwhile...half day Friday.....Nice afternoon for a blast......
I checked a bit deeper into the FAST EZ EFI system and also concluded it was not meant for any Turbo/blower applications. Seems the way it self calibrates makes an assumption that it is n/a.
As for fuel economy....I dont expect much advantage...but I do know mine is currently running quite rich throughout, so probably would gain some with either better carb set up or EFi. The main reason for considering EFi would be road manners at low (ish) revs.
Intend to keep an open mind for the moment so any further views would be welcome.
.......Meanwhile...half day Friday.....Nice afternoon for a blast......
Mr Pid said:
Supercharger is Weiand 177 running at about 7 psi....with carb on top it is running 'wet'....if i went for TBi it would remain wet....but if i went multipoint it would clearly be dry.....didnt know this was sometimes a concern.
I had considered injecting one myself. The Weiand 144 is designed for wet, so i guess the 177 is too. I have previously asked them about it. So it would have to be TBI. I don't think you'll achieve much by injecting through the blower.
Better multi-point and use a centrifugal blower.
However that is going to be VERY expensive and I suspect your low rpm manners could be down to high cam overlap as well as poor fuelling.
Set up what you have to the optimum is my 2p's worth........unless you have deep pockets of course
Better multi-point and use a centrifugal blower.
However that is going to be VERY expensive and I suspect your low rpm manners could be down to high cam overlap as well as poor fuelling.
Set up what you have to the optimum is my 2p's worth........unless you have deep pockets of course
[quote=MarkWebb]I have big cam overlap and 'nothing' is going to change the low rev manners much. I would expect a supercharged motor to have less of a cam but in the end you need to know if it is the cam or the tune causing the problem.
Hmm...............not quite 100% true Mark. The intake manifold distribution in a lopey cammed Sbc is not great at low rpm, however you could ensure all the other mechanicals and aspects of tune (not just A-F) are optimized to suit. Most of the so-called well tuned ones seem some way off..... understandably in many instances, due to spec/time/budget constraints.
Hmm...............not quite 100% true Mark. The intake manifold distribution in a lopey cammed Sbc is not great at low rpm, however you could ensure all the other mechanicals and aspects of tune (not just A-F) are optimized to suit. Most of the so-called well tuned ones seem some way off..... understandably in many instances, due to spec/time/budget constraints.
Thought I would post an update........
After some consideration of these responses I decided to go for the 'get the holley working right' before thinking about the large investment needed in EFi.
So.... got a carb rebuild kit from real steel and holley carb book from flea bay. Then spent some time reading up on Holleys while rebuilding mine. Found out lots of interesting stuff...dont consider myself an expert....but have a very good appreciation of all the various circuits in the carb, what they do and how they affect running.
Also discovered a vital piece of info regarding use of the holley with a roots type blower. With the blower the base of the carb is seeing vacuum all the time so if you use a std carb the power valve (vented to the bottom of the carb) is closed all the time causing v lean running at high power settings. So with a holley 'blower carb' the power valve is connected to an external vacuum pipe that needs to connected to the manifold below the blower. The power valve then sees true manifold vacuum and properly richens the mixture at high power demands when vacuum drops (and boost comes in on a blower application)..while keeping the mixture leaner at low throttle settings.
Anyway turns out mine has the right blower carb but the power valve pipe was blocked off. Outcome is power valve never sees any vacuum so is permenantly open causing very rich running everywhere.
Next step was to Invest in a vacuum/boost guage from flea bay also and got to do some setting up....In summary it went like this.....
Opened the secondary throttles a tiny bit at idle (they were fully closed) which allowed me to slightly close the primaries.....got much better control of idle mixture and adjusted for max vacuum....needed slightly richer idle mixture setting but closed off more of transfer slots and overall idles better with smoother pick up. With the vent baffles in place and slightly lowered float level in the secondary bowl I should be getting a slightly leaner mixture at full throttle (was v rich) and should prevent a tendancy to stall under heavy braking (usually caused by fuel sloshing out the secondary float vent and flooding the motor).
Connecting up the manifold vacuum properly for the blower carb also means the car is running leaner at low throttle settings as the power valve is properly held shut until high throttle settings/low vacuum are seen.
The result is most impressive.....still have all the power at high throttle settings but idle is improved, it doesnt want to stall under heavy breaking, part throttle pick up is much smoother, as is idle...and fuel consumption is massively reduced....from something like 10 mpg to more like 17 mpg under a mixture of driving.
So overall a happy outcome with modest outlay....have increased my knowledge of carbs and had a nice little project to boot.....
So thanks for all the input...the EFi will wait for another day !
After some consideration of these responses I decided to go for the 'get the holley working right' before thinking about the large investment needed in EFi.
So.... got a carb rebuild kit from real steel and holley carb book from flea bay. Then spent some time reading up on Holleys while rebuilding mine. Found out lots of interesting stuff...dont consider myself an expert....but have a very good appreciation of all the various circuits in the carb, what they do and how they affect running.
Also discovered a vital piece of info regarding use of the holley with a roots type blower. With the blower the base of the carb is seeing vacuum all the time so if you use a std carb the power valve (vented to the bottom of the carb) is closed all the time causing v lean running at high power settings. So with a holley 'blower carb' the power valve is connected to an external vacuum pipe that needs to connected to the manifold below the blower. The power valve then sees true manifold vacuum and properly richens the mixture at high power demands when vacuum drops (and boost comes in on a blower application)..while keeping the mixture leaner at low throttle settings.
Anyway turns out mine has the right blower carb but the power valve pipe was blocked off. Outcome is power valve never sees any vacuum so is permenantly open causing very rich running everywhere.
Next step was to Invest in a vacuum/boost guage from flea bay also and got to do some setting up....In summary it went like this.....
Opened the secondary throttles a tiny bit at idle (they were fully closed) which allowed me to slightly close the primaries.....got much better control of idle mixture and adjusted for max vacuum....needed slightly richer idle mixture setting but closed off more of transfer slots and overall idles better with smoother pick up. With the vent baffles in place and slightly lowered float level in the secondary bowl I should be getting a slightly leaner mixture at full throttle (was v rich) and should prevent a tendancy to stall under heavy braking (usually caused by fuel sloshing out the secondary float vent and flooding the motor).
Connecting up the manifold vacuum properly for the blower carb also means the car is running leaner at low throttle settings as the power valve is properly held shut until high throttle settings/low vacuum are seen.
The result is most impressive.....still have all the power at high throttle settings but idle is improved, it doesnt want to stall under heavy breaking, part throttle pick up is much smoother, as is idle...and fuel consumption is massively reduced....from something like 10 mpg to more like 17 mpg under a mixture of driving.
So overall a happy outcome with modest outlay....have increased my knowledge of carbs and had a nice little project to boot.....
So thanks for all the input...the EFi will wait for another day !
Well done.... glad you have seen some good results too.
As posted before I ve spent along time tinkering with my holley's.... I have seen 22-23 mpg on a long run on the motorway, but in order to do that you do have to cruise at 70-75, however the results are impressive. Have to say when I play and drive hard my figures will never be as good as an LS but then I havent spent 10k or so changing the motor..I just think 10k worth of fuel goes a long long way..haha
Dom
As posted before I ve spent along time tinkering with my holley's.... I have seen 22-23 mpg on a long run on the motorway, but in order to do that you do have to cruise at 70-75, however the results are impressive. Have to say when I play and drive hard my figures will never be as good as an LS but then I havent spent 10k or so changing the motor..I just think 10k worth of fuel goes a long long way..haha
Dom
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