Injector Fitting

[ThirtyThree]

Looking to get a 1000cc injectors for an RB25 after advice from a tuner, after being near impossible to find side feed bolt on 1000cc units, (if anyone knows of any that would be the greatest help!)

Now opting for a modified rail to fit a top feed injector. Problem now is, not sure if the injectors will clear the standard inlet manifold, i.e. the one that crosses over the motor, so now looking to get a greddy plenum.

Just want to know if a) anyone know where to get 1000cc injectors that will fit a 25 side feed straight bolt on?

or b) if i get top feed injectors with a modified rail, will it fit? or will I have to get an aftermarket plenum like a Greddy or Plazaman?

Any help appreciated!!!

Edited April 24, 2008 by ThirtyThree

[Adriano]

Im going out on a limb here, but i cant see any reason why you would need 1000cc injectors if you are considering using a standard inlet manifold. What power are you hoping to make? To make the sort of power that requires 1000cc injectors, it will be cheaper to fit an rb26 head than stuffing around with a 25 one.

[The Dan]

Im going out on a limb here, but i cant see any reason why you would need 1000cc injectors if you are considering using a standard inlet manifold. What power are you hoping to make? To make the sort of power that requires 1000cc injectors, it will be cheaper to fit an rb26 head than stuffing around with a 25 one.

Incorrect, it costs exactly the same to modify an RB25 head to flow exactly the same as an RB26 head, For injectors that size he would obviously be chasing 800-900rwhp so the RB26 head would need the same changes a 25 would get.

Also, the standard inlet can flow the same quantity of air as any aftermarket option. The only difference is the plenum chamber is slightly smaller (this can be changed/modified )

[JonTurpening]

If these factors are true for his application:

B.S.F.C of .55

Max injector duty cycle of 95%

With 6 injectors

He will need at least 1013.15 cc injectors to get 1000 crank shaft hp at 40psi of fuel pressure.

However, I have found on most turbocharged cars that the B.S.F.C is more around .60-.65. Also, I don't like to run any more then 80-85% duty cycle on my injectors.

[Sydneykid]

Incorrect, it costs exactly the same to modify an RB25 head to flow exactly the same as an RB26 head

Not in my experience, RB26 cams are cheaper, both new and used, there is larger choice of RB26 camshaft profiles and suppliers, RB26's have solid lifters standard, RB25's have hydraulics that have to be converted, the RB25 inlet manifold doesn't like much more than 300 rwkw, RB26 inlet manifolds have no problem at 450 rwkw, RB25 exhaust manifolds don't like much more than 300 rwkw, RB26 inlet manifolds have no problem at 450 rwk, oversized RB26 valves are cheaper than RB25 oversized valves also due to them being more common, RB25's have VVT which has to be removed for true high BHP applications, RB26's don't have VVT, aftermarket RB26 valve springs are cheaper then RB25's, RB26 head gaskets are cheaper than RB25's as they are the same as RB30's, RB26's have 12 mm head bolt holes, RB25's are 11 mm and so have to be drilled to fit the largr headstuds that a true high bhp engine demands, RB26 heads have better oil flow return to the sump then RB25's which require more machining....................

I have more if you want

Cheers

Gary

[Sydneykid]

Looking to get a 1000cc injectors for an RB25 after advice from a tuner, after being near impossible to find side feed bolt on 1000cc units, (if anyone knows of any that would be the greatest help!)

Now opting for a modified rail to fit a top feed injector. Problem now is, not sure if the injectors will clear the standard inlet manifold, i.e. the one that crosses over the motor, so now looking to get a greddy plenum.

Just want to know if a) anyone know where to get 1000cc injectors that will fit a 25 side feed straight bolt on?

or b) if i get top feed injectors with a modified rail, will it fit? or will I have to get an aftermarket plenum like a Greddy or Plazaman?

Any help appreciated!!!

You have an obvious conflict here;

1000 cc injectors = ~1000 bhp capacity

RB25 standard inlet manifold = ~500 bhp capacity

Which is it that you require?

Cheers

Gary

[ThirtyThree]

basically going off what the tuner requires for the 1000cc injectors,

he is trying to source some side feed but is having a bit of trouble so I thought Id look into other options such as the rail mod while I wait.

I also thought 1000cc is a bit big although his arguement there is something along the lines of runninng the injectors at 75 - 80% duty cycle - im no mechanic myself im just trying to go with what he says so when it comes to tuning and somethings not right I dont get the whole I told you so when he isnt happy with the 850cc's

The main thing Im trying to find out is, if I do have to change the rail, and put top feed injectors in, am I going to be screwed for clearances with the top half of the stock inlet manifold and throttle body position etc. ?????

If so I will have to go something like a plazmaman...

[The Dan]

basically going off what the tuner requires for the 1000cc injectors,

he is trying to source some side feed but is having a bit of trouble so I thought Id look into other options such as the rail mod while I wait.

I also thought 1000cc is a bit big although his arguement there is something along the lines of runninng the injectors at 75 - 80% duty cycle - im no mechanic myself im just trying to go with what he says so when it comes to tuning and somethings not right I dont get the whole I told you so when he isnt happy with the 850cc's

The main thing Im trying to find out is, if I do have to change the rail, and put top feed injectors in, am I going to be screwed for clearances with the top half of the stock inlet manifold and throttle body position etc. ?????

If so I will have to go something like a plazmaman...

How much HP are you making?

Tell me this and I will be able to help.

[ThirtyThree]

How much HP are you making?

Tell me this and I will be able to help.

about 300rwkw, but plannaing ahead as its likely to go further

[The Dan]

Not in my experience, RB26 cams are cheaper, both new and used, there is larger choice of RB26 camshaft profiles and suppliers, RB26's have solid lifters standard, RB25's have hydraulics that have to be converted, the RB25 inlet manifold doesn't like much more than 300 rwkw, RB26 inlet manifolds have no problem at 450 rwkw, RB25 exhaust manifolds don't like much more than 300 rwkw, RB26 inlet manifolds have no problem at 450 rwk, oversized RB26 valves are cheaper than RB25 oversized valves also due to them being more common, RB25's have VVT which has to be removed for true high BHP applications, RB26's don't have VVT, aftermarket RB26 valve springs are cheaper then RB25's, RB26 head gaskets are cheaper than RB25's as they are the same as RB30's, RB26's have 12 mm head bolt holes, RB25's are 11 mm and so have to be drilled to fit the largr headstuds that a true high bhp engine demands, RB26 heads have better oil flow return to the sump then RB25's which require more machining....................

I have more if you want

Cheers

Gary

There is more what?...gibberish?

When you properly set up an RB25 head, you will be using RB26 camshafts anyway. RB25 cams cost exactly the same, it's not my fault you get owned by your supplier. Like you said, the 25 will be converted to solid also.

Do you have proof that the factory manifold cannot flow more than 300rwkw? If so, then you are suggesting the head can flow more than the inlet manifold which has exactly the same port sizing?

RB25 exhaust manifolds do resist flow at 300rwkw but if you are seting up a "true high BHP application" then you wouldn't have this anyway.

Once again, your supplier must be owning you on valves as these also cost within a couple of dollars of each other. I sent an RB25 head away to Ferrea and they now stock the 25 valves.

Head gaskets are the same cost....see note on supplier above.

Head bolts, you are correct...this does cost a hundred dollars or so to have done.

You are incorrect on the oil return to the sump as the 25 has the same size return ports and one extra one from the front of the head which the 26 does not.

So the extra $1000 you have spent just to buy the 26 head with super dooper manifolds has easily been a false economy when you consider the potential of a correctly set up 25 head.

Cheers,

Daniel

[The Dan]

about 300rwkw, but plannaing ahead as its likely to go further

Then 550cc injectors will easily supply you with enough fuel.

800's are a good option for you for future imporvements if you needed them.

And on the note of duty cycle, 100% is maximum, not 95%. Some Hondas run 100% duty from factory.

It is only old design injectors that are not happy at these duty cycles.

[ThirtyThree]

Thanks for your input but does anyone have any experience with my real question?

[JonTurpening]

Not with the stock intake. I do have top feed injectors but I have a different intake. Sorry!

Edited April 25, 2008 by JonTurpening

[ThirtyThree]

Not with the stock intake. I do have top feed injectors but I have a different intake. Sorry!

Did you do the intake because it didnt fit? or just for its own benifits?

[Adriano]

There is more what?...gibberish?

When you properly set up an RB25 head, you will be using RB26 camshafts anyway. RB25 cams cost exactly the same, it's not my fault you get owned by your supplier. Like you said, the 25 will be converted to solid also.

Do you have proof that the factory manifold cannot flow more than 300rwkw? If so, then you are suggesting the head can flow more than the inlet manifold which has exactly the same port sizing?

RB25 exhaust manifolds do resist flow at 300rwkw but if you are seting up a "true high BHP application" then you wouldn't have this anyway.

Once again, your supplier must be owning you on valves as these also cost within a couple of dollars of each other. I sent an RB25 head away to Ferrea and they now stock the 25 valves.

Head gaskets are the same cost....see note on supplier above.

Head bolts, you are correct...this does cost a hundred dollars or so to have done.

You are incorrect on the oil return to the sump as the 25 has the same size return ports and one extra one from the front of the head which the 26 does not.

So the extra $1000 you have spent just to buy the 26 head with super dooper manifolds has easily been a false economy when you consider the potential of a correctly set up 25 head.

Cheers,

Daniel

Where do you get your rb25 solid lifter conversion for free?

[rb26s13]

Where do you get your rb25 solid lifter conversion for free?

in a true high hp setup were you go large cams.. the cost of the 26 and 25 still end up being the same as you have to upgrade the lifters to tomei items in the 26 head with 10.25mm lift cams and larger.. so thats 400odd.. and the rb25 solid lifters made by tomei are about the same price.. so really there is f**k all difference

the only real advantage i see from using a 26 head over the rb25 head is the fact that the 26 head setup correctly can handle 11.5mm lift were as the 25 can handle about 10.2 max(from memory)

[Adriano]

So we are all in agreeance that there is no need to fit 1000cc injectors to a stock inlet manifold.

(PS im using 272 10.2mm cams with stock solid lifters without dramas)

[rb26s13]

So we are all in agreeance that there is no need to fit 1000cc injectors to a stock inlet manifold.

(PS im using 272 10.2mm cams with stock solid lifters without dramas)

interesting.. i was using 10.25 260 procams and needed the tomei lifters to get right clearance cause of the smaller basecircle..

[rb26s13]

and agreed.. 300rwkw and maxing out 850's.. something is wrong wat fuel pump setup do you have? wat fuel reg?

[R338OY]

Yes