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Carb 7 Port Head


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#1 the.stroker

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Posted 24 September 2018 - 06:12 PM

I’ll be installing a 7 port head over the winter, running two Weber carbs.
So much choice from the usual suspects, SC, MED, Mini sport.

Any recommendations from those running a 7 port set up?

The current MED engine is highly tuned and kicking out 119bhp, always after more though.

The SC is tempting me....

https://www.speciali...inder-head.html

#2 mk1leg

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Posted 24 September 2018 - 06:49 PM

go down the fuel injection route a lot less hassle

i'm running 4 suzuki bike carbs but would defo go down the injection route



#3 stevegrabba

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Posted 05 November 2018 - 10:11 PM

I have an SC 7 port, fuel injected and I'm thinking of switching to carbs.  For me there are too many corrective factors involved when running fuel injection via an ecu and getting all of them to agree which each other on any given day is a challenge.  Just jet and set your carbs right to start with and the job is done.



#4 matty...

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Posted 05 November 2018 - 11:10 PM

Ive made few different inlets now to fit Webers to the SC 7 port heads. Not much room in a round nose though! A set of Mikhuni or Keihin flat slide carbs would be my preference.

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#5 nicklouse

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Posted 05 November 2018 - 11:58 PM

mappable and programmable is way better than carbs the only issue is you need to have enough sensors to give the info that the system needs to make the most of it.

 

if i was doing a fresh build then ignition and injection would be fully mappable.



#6 Midas Mk1

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Posted 06 November 2018 - 08:00 AM

I have an SC 7 port, fuel injected and I'm thinking of switching to carbs.  For me there are too many corrective factors involved when running fuel injection via an ecu and getting all of them to agree which each other on any given day is a challenge.  Just jet and set your carbs right to start with and the job is done.

 

Get it mapped by someone who knows the software and tuning inside out, such as Chris @ EFI Parts, or likewise.  The average joe wont set it up aswell, be a mile away. I'd deffo stick with my sc injection..  

 

3 hours on a dyno and it's like night.. and well.. 


Edited by Midas Mk1, 06 November 2018 - 08:01 AM.


#7 stevegrabba

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Posted 06 November 2018 - 09:13 AM

 

I have an SC 7 port, fuel injected and I'm thinking of switching to carbs.  For me there are too many corrective factors involved when running fuel injection via an ecu and getting all of them to agree which each other on any given day is a challenge.  Just jet and set your carbs right to start with and the job is done.

 

Get it mapped by someone who knows the software and tuning inside out, such as Chris @ EFI Parts, or likewise.  The average joe wont set it up aswell, be a mile away. I'd deffo stick with my sc injection..  

 

3 hours on a dyno and it's like night.. and well.. 

 

 

I'm running the RE13OT cam so contacted Graham Russel for his advice regarding the ignition advance curve.  The base map by SC was a mile off, and dubious if it was ever based on the RE13!! I plotted his advice into the base maps, no probs at all for 3 curves over the full 16 x 16 positions and had a good what circuit, mid throttle and 'vacuum simulated advance' for cruise etc.  I then did the same for base fuel maps, to give near optimum AFR readings that I would want for the 3 types of driving...checked through a second wide band lambda..based on a combination of known SU needle profiles (ratios for the change for needle dias across the 13 positions) and known DCOE jetting too for a similar cam. I cross referenced actual AFR readings against the primary closed loop reference values, and pre-set target lambda values. The car was running great over a 2 or 3 month period, all AFR values were as near as dam it what I wanted.  Until autumn came and then one day I noticed whenever I was driving in cold air due to a side of the road which didn't see the sun, or high up in the N. Yorks moors...the AFR reading started to run rich (9:1 or 10:1), and I got occasional pre-ignition misfires etc.  So I was then on to making sure the air temperature fuel compensation values were't crazy, and changing injector pulse rates because of a 5 or 10 deg change in air temp and density etc.

 

To try and take care of the oil and running temps I fitted a thermostatically opening oil cooler.  Car run great and then when the oil temp thermostat opens, oil temp fuel correction values kick in again and I get a stutter or two, until the temp stabilizes again.  But if I go through any cold air at the same time, and it really doesn't like it because one can be enriching whilst the other is trying to weaken.  Let alone putting your foot down and the acceleration enrichment kicks in at the same time.

 

I've ended up disabling most of the corrective values for anything other start up, stabilisation of idle and once beyond an oil temp of approx 75 to 80C...they are all pretty much zero correction, and I'm then just simulating exactly what I would have got with a dizzy and carb controlled fueling.  And she idles well, no stalling and runs like a dream now! 

 

Ok, I could stick it on a trailer and pay the 'man with the van' £300 for a day out for taking it to a good rolling road operator.  Pay the rolling road operator £500 ish for a full remap, but at the end of the day its a mini.  I've worked on mini's for 30 years, and one reason for having a mini is so that I can work on it myself.  I've set the many values myself with Sunday morning runs out and about with a laptop, based on fueling and ignition timing, and cams that I've successfully used for years.   As you can see, I'm by no means a technophobe, but with carbs once set, carbs aren't nearly as sensitive and once you have a good ignition curve, the right needle and jet set up...that's it.  But not with fuel injection and so many corrective sensors, and at least a dozen more than the basics which I have mentioned above here...that can and do fail at times also. 

 

It's horses for courses, and respectfully each to their own but I'm personally a carb man!!


Edited by stevegrabba, 06 November 2018 - 09:45 AM.


#8 stevegrabba

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Posted 06 November 2018 - 09:20 AM

Ive made few different inlets now to fit Webers to the SC 7 port heads. Not much room in a round nose though! A set of Mikhuni or Keihin flat slide carbs would be my preference.

Some lovely craftsmanship there mate!!  That reminds me, one of the issues with the SC inlets to throttle bodies, they are too short!!  Yes they fit in the round nose, but due to the short length its difficult to get stability of the fueling mix and as we all know from the long inlets used with 5 ports and webbers, the longer the better for most cars including the A series.  What do you charge for those inlets, I could be very tempted?


Edited by stevegrabba, 06 November 2018 - 09:45 AM.


#9 Bat

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Posted 06 November 2018 - 10:43 AM

Hi,

Injection everytime!

Get the right ECU, tell it what sensors you've got then let it map itself. Hook your laptop up and log everything then sit back on the sofa and make your mods.

If set up to the sensors correctly the ECU should be making the compensations correctly.

With throttle bodies you need to run alpha N for load which will use the TPS until the vacuum gets stable then it blends into using the MAP sensor.

Obviously with a wilder cam you can map in loads of advance when off cam to gain more torque.

Cheers  :proud:


Edited by Bat, 06 November 2018 - 10:44 AM.


#10 stevegrabba

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Posted 06 November 2018 - 12:38 PM

Hi,

Injection everytime!

Get the right ECU, tell it what sensors you've got then let it map itself. Hook your laptop up and log everything then sit back on the sofa and make your mods.

If set up to the sensors correctly the ECU should be making the compensations correctly.

With throttle bodies you need to run alpha N for load which will use the TPS until the vacuum gets stable then it blends into using the MAP sensor.

Obviously with a wilder cam you can map in loads of advance when off cam to gain more torque.

Cheers  :proud:

Interesting...but remember throttle bodies on a 7port and there is minimal vacuum, and even less with a performance cam present.  Its not easy to get sufficient vacuum to get the stability that you mention.  Just a thought...



#11 Bat

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Posted 06 November 2018 - 01:13 PM

Hi,

That's why it uses the TPS at low revs. You just take a vac signal from each port, join them together and connect to the MAP sensor. The ECU should have settings for you to define the changeover points. No different to what you'd do with a BMW K head.

Cheers  :proud:



#12 Bat

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Posted 06 November 2018 - 07:54 PM

 

 

I have an SC 7 port, fuel injected and I'm thinking of switching to carbs.  For me there are too many corrective factors involved when running fuel injection via an ecu and getting all of them to agree which each other on any given day is a challenge.  Just jet and set your carbs right to start with and the job is done.

 

Get it mapped by someone who knows the software and tuning inside out, such as Chris @ EFI Parts, or likewise.  The average joe wont set it up aswell, be a mile away. I'd deffo stick with my sc injection..  

 

3 hours on a dyno and it's like night.. and well.. 

 

 

I'm running the RE13OT cam so contacted Graham Russel for his advice regarding the ignition advance curve.  The base map by SC was a mile off, and dubious if it was ever based on the RE13!! I plotted his advice into the base maps, no probs at all for 3 curves over the full 16 x 16 positions and had a good what circuit, mid throttle and 'vacuum simulated advance' for cruise etc.  I then did the same for base fuel maps, to give near optimum AFR readings that I would want for the 3 types of driving...checked through a second wide band lambda..based on a combination of known SU needle profiles (ratios for the change for needle dias across the 13 positions) and known DCOE jetting too for a similar cam. I cross referenced actual AFR readings against the primary closed loop reference values, and pre-set target lambda values. The car was running great over a 2 or 3 month period, all AFR values were as near as dam it what I wanted.  Until autumn came and then one day I noticed whenever I was driving in cold air due to a side of the road which didn't see the sun, or high up in the N. Yorks moors...the AFR reading started to run rich (9:1 or 10:1), and I got occasional pre-ignition misfires etc.  So I was then on to making sure the air temperature fuel compensation values were't crazy, and changing injector pulse rates because of a 5 or 10 deg change in air temp and density etc.

 

To try and take care of the oil and running temps I fitted a thermostatically opening oil cooler.  Car run great and then when the oil temp thermostat opens, oil temp fuel correction values kick in again and I get a stutter or two, until the temp stabilizes again.  But if I go through any cold air at the same time, and it really doesn't like it because one can be enriching whilst the other is trying to weaken.  Let alone putting your foot down and the acceleration enrichment kicks in at the same time.

 

I've ended up disabling most of the corrective values for anything other start up, stabilisation of idle and once beyond an oil temp of approx 75 to 80C...they are all pretty much zero correction, and I'm then just simulating exactly what I would have got with a dizzy and carb controlled fueling.  And she idles well, no stalling and runs like a dream now! 

 

Ok, I could stick it on a trailer and pay the 'man with the van' £300 for a day out for taking it to a good rolling road operator.  Pay the rolling road operator £500 ish for a full remap, but at the end of the day its a mini.  I've worked on mini's for 30 years, and one reason for having a mini is so that I can work on it myself.  I've set the many values myself with Sunday morning runs out and about with a laptop, based on fueling and ignition timing, and cams that I've successfully used for years.   As you can see, I'm by no means a technophobe, but with carbs once set, carbs aren't nearly as sensitive and once you have a good ignition curve, the right needle and jet set up...that's it.  But not with fuel injection and so many corrective sensors, and at least a dozen more than the basics which I have mentioned above here...that can and do fail at times also. 

 

It's horses for courses, and respectfully each to their own but I'm personally a carb man!!

 

Hi,

Sounds like you had icing problems, just like you'd get with a carb stuck out in the cold air flow.

Cheers  :proud:



#13 stevegrabba

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Posted 06 November 2018 - 10:25 PM

 

 

 

I have an SC 7 port, fuel injected and I'm thinking of switching to carbs.  For me there are too many corrective factors involved when running fuel injection via an ecu and getting all of them to agree which each other on any given day is a challenge.  Just jet and set your carbs right to start with and the job is done.

 

Get it mapped by someone who knows the software and tuning inside out, such as Chris @ EFI Parts, or likewise.  The average joe wont set it up aswell, be a mile away. I'd deffo stick with my sc injection..  

 

3 hours on a dyno and it's like night.. and well.. 

 

 

I'm running the RE13OT cam so contacted Graham Russel for his advice regarding the ignition advance curve.  The base map by SC was a mile off, and dubious if it was ever based on the RE13!! I plotted his advice into the base maps, no probs at all for 3 curves over the full 16 x 16 positions and had a good what circuit, mid throttle and 'vacuum simulated advance' for cruise etc.  I then did the same for base fuel maps, to give near optimum AFR readings that I would want for the 3 types of driving...checked through a second wide band lambda..based on a combination of known SU needle profiles (ratios for the change for needle dias across the 13 positions) and known DCOE jetting too for a similar cam. I cross referenced actual AFR readings against the primary closed loop reference values, and pre-set target lambda values. The car was running great over a 2 or 3 month period, all AFR values were as near as dam it what I wanted.  Until autumn came and then one day I noticed whenever I was driving in cold air due to a side of the road which didn't see the sun, or high up in the N. Yorks moors...the AFR reading started to run rich (9:1 or 10:1), and I got occasional pre-ignition misfires etc.  So I was then on to making sure the air temperature fuel compensation values were't crazy, and changing injector pulse rates because of a 5 or 10 deg change in air temp and density etc.

 

To try and take care of the oil and running temps I fitted a thermostatically opening oil cooler.  Car run great and then when the oil temp thermostat opens, oil temp fuel correction values kick in again and I get a stutter or two, until the temp stabilizes again.  But if I go through any cold air at the same time, and it really doesn't like it because one can be enriching whilst the other is trying to weaken.  Let alone putting your foot down and the acceleration enrichment kicks in at the same time.

 

I've ended up disabling most of the corrective values for anything other start up, stabilisation of idle and once beyond an oil temp of approx 75 to 80C...they are all pretty much zero correction, and I'm then just simulating exactly what I would have got with a dizzy and carb controlled fueling.  And she idles well, no stalling and runs like a dream now! 

 

Ok, I could stick it on a trailer and pay the 'man with the van' £300 for a day out for taking it to a good rolling road operator.  Pay the rolling road operator £500 ish for a full remap, but at the end of the day its a mini.  I've worked on mini's for 30 years, and one reason for having a mini is so that I can work on it myself.  I've set the many values myself with Sunday morning runs out and about with a laptop, based on fueling and ignition timing, and cams that I've successfully used for years.   As you can see, I'm by no means a technophobe, but with carbs once set, carbs aren't nearly as sensitive and once you have a good ignition curve, the right needle and jet set up...that's it.  But not with fuel injection and so many corrective sensors, and at least a dozen more than the basics which I have mentioned above here...that can and do fail at times also. 

 

It's horses for courses, and respectfully each to their own but I'm personally a carb man!!

 

Hi,

Sounds like you had icing problems, just like you'd get with a carb stuck out in the cold air flow.

Cheers  :proud:

 

Ha ha...my lucky run of never having anything near as severe with carb icing is officially over then, and it must have even iced my oil temperature correction values too ......how unlucky is that!!  It won't beat me though, I will set the little devil with the right values.  ha ha



#14 Bat

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Posted 07 November 2018 - 08:48 AM

Hi,

I've had it myself with a 45 dcoe though. I thought that as it was at the back the heat from the engine would keep it warm!

Had to put in a piece of flexible ducting from the exhaust manifold to the air filter during winter.

I've not heard of an aftermarket ECU taking oil temperature measurements.

Coolant and air temp would be the only ones I would worry about.

Cheers  :proud:



#15 stevegrabba

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Posted 07 November 2018 - 09:25 AM

Hi,

I've had it myself with a 45 dcoe though. I thought that as it was at the back the heat from the engine would keep it warm!

Had to put in a piece of flexible ducting from the exhaust manifold to the air filter during winter.

I've not heard of an aftermarket ECU taking oil temperature measurements.

Coolant and air temp would be the only ones I would worry about.

Cheers  :proud:

Carb/injector icing effect - The surprising bit for me was that I'd been out in the car and was maybe 30 mins into a drive, so well up to temp of 85 to 90C.  It was late September, so lets say 18 to 20 deg in the sun, and maybe 13 to 15 deg in the shade.  Its nothing of a difference really!!  The car would start running off-tune and drop from an AFR of  mid 12's, to 9's or 10s within within 4 or 5 seconds of entering a shaded road.  Over the tops of the moors and off the coast it was different, and I could see the engine temp drop to maybe 75C, hence sustained cold air intake.

 

Interesting idea about the flexible ducting....I might have to develop something to give more control over the air temperature, and less variation.






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