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The Skid Factory - episode discussion


k31th

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Thanks for the reply.

 

Sorry bad choice of words. Was more referring to the standard motor/internals.

 

As you said maybe building a motor later on. So no real disadvantages running a bigger injector for now?

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It'll be fine on e85 but would likely have low pw issues on 98. Not ideal but not the end of the world either. 

 

To clarify my 70% idc estimate, head over to the injector dynamics fuel flow calculator and see what you get when you plug in a 3 bar base fuel pressure, 0.78 lambda and 25 psi boost pressure.

 

Generally you wouldn't choose an injector that big but there are reasons that you might do so, such as headroom or just having them lying around. 

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It is a good general question. I've often wondered why people put monster injectors in 98 cars with moderate power, when surely the cost and idle/cruise characteristics would be better with something smaller.

 

Probably a mix of bragging rights, shops wanting to upsell to a more expensive product and shops knowing that customers will be back for more power later.

 

In this case though, yeah it's E85 and the package is clearly aiming at considerable power.

 

Edit: haha what the heck was with the Family Guy bit at the start??

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yeah; plenty of shops spruik 1000cc injectors at a minimum, seemingly because they had easy to tune capabilities plus the extra mark up of the upsell.

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And, which is fair enough, for copy and paste ability. If I was tuning every day I'd rather be able to quickly do an outstanding job on a couple of different injectors rather than spending more time doing an ok job on lots of various injectors.

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indeed... I'm not 100% familiar with the scaling/flow/spray requirements for different injectors, but it can't be that hard, can it :idunno:

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That's reminded me - I did some scaling for Bosch 968s as I was about to buy them for the BA. The data available was for a range of fuel pressures, but not 4 bar. I wanted to go through the process of doing it myself rather than just copying from someone else, so did some calcs and then was going to dial in on the road.

I'll post them up later, maybe in the DIY tuning thread, to see if the approach I used was correct. I basically graphed the data I had and used a line of best fit to work out 4 bar values.

Won't use the values now as I'll use a different injector in the FG (maybe Bosch 57lb or something). Would still be useful to know if I'm understanding the concepts correctly though.

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1 hour ago, k31th said:

yeah; plenty of shops spruik 1000cc injectors at a minimum, seemingly because they had easy to tune capabilities plus the extra mark up of the upsell.

Big jump in price from 1000cc to 1300cc to 1700cc. 1000cc will see you over 500 on e85.  I think about 550 it should be 1300s and then larger Iam not sure.

 

BUT just choose the smallest injectors for your ultimate power goal. But these days large injectors can idle nice , not like the old days.

 

Tuners use the same 1000cc as they have all the tuning tables calculated so easier to tune.

 

Having raced cars and bikes, its not just the flexing of the car /bike but vibrations from high RPM that fracture components. Rubber mounting items is an old trick, which seems to have been forgotten these days. BUT not buy the older guys that really know...

 

FULLY rubber mounted.

 

DSC_4170.jpg

Edited by arronm
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My bosch 1000's were at 50% at 17.25psi/6100rpm on 98 with 0.8ish lambda. No idle issues running stoich on 98 and still had something left at 21psi on e85 (I didn't check how much though).

 

That will give some idea about the necessity of having "1000cc" injectors. Haha I recommend that size cos they work on 98 and there's headroom for e85 but they are overkill for most cars.

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