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Fuel Injection Conversion


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#1 miniBrain

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Posted 11 September 2015 - 01:24 PM

Hi,

 

I finally got fed up with trying to tune SU carbs for non-standard configurations (I'm too mean to hire a rolling road session every time I make a change) so decided to switch over to fuel injection, based on the SPi throttle body and manifold:

 

IMGP8956.jpg

 

I developed my own ECU over that last 6 months or so and eventually got the car running really well - far better that I've ever had on a carb engine. There's a detailed description here:

 

http://www.just-tech...lopment_145#145

 

If you've been wondering about Megasquirt or similar, then I'd say go for it - its worth it even just to get rid of the choke.

 

Incidentally the car's got a 1098 engine in it at the moment - I wonder how many fuel injected 1098 engines there are? 

 

 



#2 Black.Ghost

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Posted 11 September 2015 - 02:19 PM

Yes! I like this a lot. I have had two SPi Coopers (one I still have) and I love the injection system. My understanding is not that detailed, but the reliability of it, the ease with which both cars started on the coldest of mornings - I love the SPi set up. The only real downside is the comparatively cluttered engine bay when compared to a nice clean carb set-up. 

 

If you had a full set-up that was bolt on, with different map tuning options, you could potentially make a little extra cash from the kits as well. 



#3 miniBrain

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Posted 11 September 2015 - 04:03 PM

I'm going to try out bike throttle body injectors and I have other engines to test it with, so maybe if it proves flexible &  reliable I could think about a kit. The ECU cost me less than £50 in parts, so it could be a cheap way to get Fuel Injection :shifty:  



#4 Gr4h4m

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Posted 11 September 2015 - 07:58 PM

Very impressed with all your design and build from scratch!

#5 miniBrain

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Posted 11 September 2015 - 08:13 PM

Very impressed with all your design and build from scratch!

 

Thank you   ;D



#6 Anthony30

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Posted 11 September 2015 - 08:15 PM

Charge robbing is a huge issue with the SPI system, some say It's worse than a single SU set-up. Siamese port injection would solve this, but not worth the headache IMO. A 7/8 port head is the only solution. It would be easier to turbo with the SPI system though, very accurate and, relatively, easy to tune. Interesting build. Post some clips of it running. :highfive:



#7 mini13

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Posted 11 September 2015 - 10:24 PM

its not a huge problem, it can work pretty well. basically it will work as an electronic carb

 

although it is a huge problem on an MPI.



#8 miniBrain

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Posted 12 September 2015 - 12:07 AM

its not a huge problem, it can work pretty well. basically it will work as an electronic carb

 

although it is a huge problem on an MPI.

 

An electronic carb is exactly what the SPi and any single point injection system is. Springs, needles, waxstats, damper fluids, etc of an SU replaced by a computer  :ohno:



#9 mini13

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Posted 12 September 2015 - 10:38 AM

yeah, and thats why it works, although beware of "SPI" systems with multiple  injectors in the throttle body, they dont always give an even fueling throughout the engine cycle.

 

the problem comes when you try to make injectors inject according to each cylinder. you end up skewing injector timing to try to get the right fuel to each cylinder. not somthing I could be bothered with to be honest.



#10 Fast Ivan

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Posted 12 September 2015 - 01:02 PM

Nice work and looks to be a good write up as well, I'll have a better read when I get a chance

#11 miniBrain

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Posted 12 September 2015 - 01:56 PM

yeah, and thats why it works, although beware of "SPI" systems with multiple  injectors in the throttle body, they dont always give an even fueling throughout the engine cycle.

 

the problem comes when you try to make injectors inject according to each cylinder. you end up skewing injector timing to try to get the right fuel to each cylinder. not somthing I could be bothered with to be honest.

 

You often see standard SPi's doing pretty well against modded carb engines in the dyno trials in the Mini World mag. That's why I went the SPi route - as you say dual port injection probably not worth the bother.



#12 miniBrain

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Posted 12 September 2015 - 01:57 PM

Nice work and looks to be a good write up as well, I'll have a better read when I get a chance

 

Thank you!  :proud:



#13 miniBrain

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Posted 12 September 2015 - 02:53 PM

Charge robbing is a huge issue with the SPI system, some say It's worse than a single SU set-up. Siamese port injection would solve this, but not worth the headache IMO. A 7/8 port head is the only solution. It would be easier to turbo with the SPI system though, very accurate and, relatively, easy to tune. Interesting build. Post some clips of it running. :highfive:

 

Here's a clip -

 

 

Nothing exciting to see in the video, except now I can mash the pedal to the floor at any time and the engine just keeps accelerating without complaint. There's probably no gain in power but driveability is much much better.


Edited by miniBrain, 12 September 2015 - 02:54 PM.


#14 Spiffingly Good

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Posted 12 September 2015 - 03:43 PM

Top work! I really like this, having a SPI myself I can even see the benefits of replacing the stock ECU for tuneability.



#15 Gr4h4m

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Posted 12 September 2015 - 05:09 PM

 

Charge robbing is a huge issue with the SPI system, some say It's worse than a single SU set-up. Siamese port injection would solve this, but not worth the headache IMO. A 7/8 port head is the only solution. It would be easier to turbo with the SPI system though, very accurate and, relatively, easy to tune. Interesting build. Post some clips of it running. :highfive:

 

Here's a clip -

 

 

Nothing exciting to see in the video, except now I can mash the pedal to the floor at any time and the engine just keeps accelerating without complaint. There's probably no gain in power but driveability is much much better.

 

 

 

I'm still super impressed that all this is built from nothing.... very good esp having to write the software etc.






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