I'm going to replace my injectors soon and I would like to up grade to more of a race application.

 

you seem to want to 'upgrade' every corner of your s type.
This isnt a tuner car, and even if it was, throwing parts at a car for no purpose is a waste of time and money.

In the aftermarket world of fuel injectors, the main purpose of 'upgrading' (usually to a higher flow rate) is to facilitate more fuel flow to support more power through more airflow. Not to mention, in most cases, you need some form of tuning to compensate for adding higher flow injectors.

Seeing your s type is mostly stock, stick with stock or stock replacement units.

 

The 4.2 NA has highish compression already so messing would be risky.

 

Why??

Are you having problems? Jaguar designed the engine for 400HP. Have you changed this?
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Candy maybe it would help if you put the details of your car into your signature.

After going back through your posts, I see that you have a Naturally Aspirated 4.2L, non-R, non-Supercharged...

According to the parts catalog, the N/A & the S/C actually use different injectors.
So if you wanted more flow (can't imagine why, unless your putting a 200-shot of NOS on the car) then the S/C injectors would be the first thing to look at.

Avos uses stock 4.2L S/C injectors on his car, and it's 630HP...and it hasn't maxed them out...

 

As I recall it's a 4.2 (possibly 4.0) NA, not an STR...

 

The stock injectors are more than capable of proving all the flow the engine could possibly require. More flow would not equate to more power.

 

Please leave your car alone.....

 

Sounds way easier and cheaper just to buy an STR.

 

Candy, IDK if this will help, but maybe you can contact these guys and clue them in with what you want to do:

https://www.jaguarforums.com/forum/x...jectors-82775/

 

Has anybody had their injectors cleaned or flow balanced? It's only about $18 each to have them cleaned and balanced.

Might help more than trying to put bigger ones in?
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Using a bigger injector does nothing for performance and can screw you on performance depending on the size. Ecu are tuned for a certain cc range, go above that and youll end up with a rich engine out of the adjustment range of the ecu which is 25%. As has already been said, if youre not adding something like a turbo or sc, you have no reason to change injectors period. If you want good performance send them out to www.injectorrx.com to be cleaned and check balance. You cannot change balance of injectors to match majically. When he gets injectors from race teams or people concern about identicle flow rates. They send him large quantities to flow them all and put together matched sets. And for most applications this is not even needed. But it does show that even new injectors do not flow the same rates or close to their ratings. So thinking that buying a new set will be the answer to matched flow is a misnormer also. Clean, rebuild, and flow check yours and be done. Anything past that is a waste unless bench racing then of course bigger is better and is always the answer

 

But can I expect any gains? I think it's a good idea and can see how it would smooth out the idle and the engine in general.
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If your existing set was somehow mismatched to the point of causing a rough idle, yes.

 

the other thing youll do with a bigger injector is forget about correct mpg computing from the ecu. it is calcualted on flow rates and pulse width for what came on the car. put bigger injectors in and SUDDENLY your mpg number in the trip computer will go way up. They wont really, so the only way to acuratly calc is to do the math. And your miles to empty and range will also be off