Can I use sp2 injectors in sp1 throttle bodies? I know (have read) that VFRs can use later model injectors, even that later model injectors are the same as Honda car injectors and can be had at auto parts stores.

I did a search and found the question, but not the answer.

No they will not work

Okay, I believe you that they will not work, but I would really like to know why.

Do you know Terry Spell, also in Henderson? I was the slowest member of his endurance race team in Texas.

Thanks for any info on why the injectors won't work. Robert

in general -
any two different injectors, even if they flow the same amount of fuel per unit of time, have different characteristics such as latencies, voltage compensations, etc. it is also possible that the sp1 and sp2 injectors have different flow rates, resulting in different scalings.

ultimately, these sorts of things can be adjusted for. i'm not familiar with how robust the powercommander is in compensating for injectors, but it is not entirely accurate to say that injector X won't work for an application. more precisely is whether or not you or your tuner can make injector X work for your application.

I have done this.The SP2 injectors are different in the way they seal in the throttle bodys, so I made some custom seats to allow the fitment.It fired right up and idled nice, but from about 2500-5500rpm the fueling was bad.After a couple of hours making adjustments on the power commander (using a wide band air/fuel meter,and seat of the pants dyno:)), I can say that there was no increase in performance.Maybe a proper dyno session will extract more horsepower, but I doubt it will be much.So I would say the standard SP1 injectors in a SP1, with a power commander are just fine.

I put up a photo of the sp1/sp2 injectors on the fireblades forum.

http://www.fireblades.org/forums/honda-rc51/90054-sp2-injectors-into-sp1.html

I have done this.The SP2 injectors are different in the way they seal in the throttle bodys, so I made some custom seats to allow the fitment.It fired right up and idled nice, but from about 2500-5500rpm the fueling was bad.After a couple of hours making adjustments on the power commander (using a wide band air/fuel meter,and seat of the pants dyno:)), I can say that there was no increase in performance.Maybe a proper dyno session will extract more horsepower, but I doubt it will be much.So I would say the standard SP1 injectors in a SP1, with a power commander are just fine.

I put up a photo of the sp1/sp2 injectors on the fireblades forum.

These injectors are made by Denso. They are different animals and remember, the ECU controls the injectors output.The construction or assy process, the injector for the SP2 is set up to accomodate the bigger intake manifold. (Not to mention the needle valve, valve seat, spring etc will be different mechanically.)

Yes they are different, slightly in fuel delivery,but can be made to work with a power commander:).

Yes they are different, slightly in fuel delivery,but can be made to work with a power commander:).

They will for a while....if the injectors duty cycle is different, you will wear out the springs faster....ah what do I know, I have only been building injectors for 20 years now....:rolleyes:

Seeing as I didnt get any real world improvement, I put the standard 4 hole injectors back in.If I were to leave them in, I would have put in a SP2 ECU, thanks for the advice though:)