EFI upgrade of k-jetronic on GTSi | Page 2 | FerrariChat

EFI upgrade of k-jetronic on GTSi

Discussion in '308/328' started by Andyinfrance, Jul 22, 2023.

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  1. mk e

    mk e F1 World Champ

    Oct 31, 2003
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    At idle getting the fuel fully vaporized and mixed is a challenge so most everyone times the injection pulse to spray right after the intake valve closes. That lets the fuel hit the back of the hot intake valve and sit on the hot port walls as long as possible getting all of it vaporized. That makes the engine the cleanest and most efficient it can be

    That is not ideal for making hp though because you are not using the vaporizing fuel to cool the incoming air, so for hp the goal is to spray into the moving air charge and pick injectors large enough so you don't need more than about a 35-40% duty cycle. There is usually a table to control what crank position injection starts or end at under different conditions.

    .....which then means the ideal injection pulses are REALLY short and hard to control. To fix that you need higher resolution in the fuel math, better accuracy in the processor, and fuel pressure and tamp sensors, and fully characterized injectors and and ecu that can accept the additional data.

    Or you size the injectors for more like 80% DC to make low power control easier since that is where a street car spends 98+% or its time and just don't think about the couple % of hp you might be giving up
     
  2. mk e

    mk e F1 World Champ

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    Forgot the injector angle. For the street the injectors want to be as close to intake valve as possible and pointing toward the valve as best as possible. It was never clear to me why the odd angle on the 2V setups but they changed it with the QV and 328.

    That said, you don't always get the injector placement you'd prefer.....and it doesn't make a ton of difference. You can end up with an idle that is higher or slightly rough but how would you ever know on a 1 of 1 install? I built a few blower intakes for QV engines and had no choice but to point the injectors at about ax30 degree angle to the port wall but they ran and idled well...they probably would have struggled to meet OEM emissions but I never tested that
     
  3. Andyinfrance

    Andyinfrance Karting

    Dec 29, 2019
    86
    France
    That’s exactly the though I’m having to find a set of flexible hoses that go to the injectors, I’m sure they can be made to look ok, seems a sensible solution. Anyone made up flexi hoses for injectors and what connectors are needed?


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  4. Andyinfrance

    Andyinfrance Karting

    Dec 29, 2019
    86
    France
    Don’t some of the injectors have angled spray patterns to one side so they could be directed better towards the intake valves? Maybe that could help on the 2V, I haven’t taken it apart yet to see what sort of angle it’s at in comparison to the intakes


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  5. mk e

    mk e F1 World Champ

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    There are different spray cone angles but that is the shape of the cone, not an angle of the cone to the axis of the injector.

    There are also dual cone injectors for 4V setups but I've never tried them.
     
  6. smg2

    smg2 F1 World Champ
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    Yup...

    Many many times like Mark.

    The odd 2V injector angle is due to the angle of the runner in the head because the water jacket and ports are different from the 4V.

    I made injector rails for the modern injectors by hand bending and brazing stainless tubing, machined cups and distro blocks. Loads of work and unfortunately on the costly side. The 2V was/is the biggest PITA to make rails for.

    Also made adapters so that nothing was modified on the oem part. The wrench in the works is that injectors today are molded plastic, the old steel bodies are custom and touch more expensive. The 4V gets the love as bmw uses a Bosch injector with an Xt nozzle, in other words the injector has a long reach nozzle like the CIS one.

    Pics to follow.

    I'm working on development of a replacement intake runner set for the 2V to utilize molded injectors and a straight forward rail. There would also be the replacement of the intake plenum. That's been sorted thankfully.

    We are utilizing more and more 3D printing and currently team with a facility that prints for DoD contracts.

    Ok I'll dig up pics
     
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  7. smg2

    smg2 F1 World Champ
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    I have, they work great and are a touch easier to control afr during idle and cruise. WOT makes zero difference.
     
  8. mk e

    mk e F1 World Champ

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    I make extensive use of additive manufacturing as well :D
     
  9. Andyinfrance

    Andyinfrance Karting

    Dec 29, 2019
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    France
  10. smg2

    smg2 F1 World Champ
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    Join the dark side!

    I really really wanted one of my boys to get into material sciences... They didn't. That area is growing due to additive mfg. It's gotten to where it's possible to print circuits in parts....:eek::cool:... But that's still in dev.
     
  11. smg2

    smg2 F1 World Champ
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  12. mk e

    mk e F1 World Champ

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    Are you working on a QV? If so maybe? As I said, I've never tried them so I just don't know how much difference they would make. I do my 4V v12 engine idles smoothly at 700 rpm with 1000cc single cone injectors so I've just never seen a reason to play with stuff like that.....but who knows what in missing out on?
     
  13. Andyinfrance

    Andyinfrance Karting

    Dec 29, 2019
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    Sorry not a QV it’s a 2V 1981 GTSi


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  14. smg2

    smg2 F1 World Champ
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    Dang it... Just got that...

    Does welding count?:p
     
  15. smg2

    smg2 F1 World Champ
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    The split cone spray wouldn't do much of anything for the 2V. But that is the correct Bosch body for getting the nozzle into the air stream.

    But there's a catch.. Always is. The 2V uses a threaded insert to hold the stock injector. The new molded injectors will require an adapter that can hold them and screw into place... Yeah haven't sorted that out as yet. The later 4V uses an internal clip that makes those easy to adapt.

    Std single cone spray is fine for the 2V in any case.
     
  16. Andyinfrance

    Andyinfrance Karting

    Dec 29, 2019
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    Someone recommended an adapter from a Skyline that could work with these injectors?

    Raceworks FSA-501BK4



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  17. smg2

    smg2 F1 World Champ
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    Not familiar with the skyline setup... That would be neat if they do.
     
  18. mk e

    mk e F1 World Champ

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    It does count!

    Whack off the old wrong bung than weld up the hole and new more useful bugs on. Maybe a couple more to bolt the fuel rail to and DONE.

    Then add a couple bugs to the TB mount a TPS to and that's done.

    Keep it simple.
     
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  19. smg2

    smg2 F1 World Champ
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    It's funny I was just thinking... Can you believe we've been at this for 20yrs or more... Talk about when a hobby gets outta control:D
     
  20. mk e

    mk e F1 World Champ

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    In a couple months I'll be at 16 years on the same stupid engine :(:mad::oops:
     
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  21. smg2

    smg2 F1 World Champ
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    I don't know that I'd call it "the same engine":p
    Iterations and order revisions, beta #X...

    But think of the education! You hold a doctorate in one man R&D on a shoestring budget.. write a book on it, the highs!, the lows, the suspense!
     

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