Injectors Size and HP

[Lextreme II]

Can anyone calculate the max bhp of 8 680 cc/min injectors would be produce. Assuming its operating at 90%.

 

[rarson]

Based off my 2.0L DOHC turbo 4-cylinder, I would say at least 800 horsepower.

 

[Peewee]

Yeah, I'd be guessing the 800-1000hp range.

 

[Zuffen]

680cc should be fun to make idle.

 

[SprinterTRD]

Rule of thumb is you need 5cc to make 1HP
so 680/5=136HP per injector
*.90 =122.4
*8=979.2Hp

 

[rarson]

680cc should be fun to make idle.

With the 4g63 and DSMLink, I've seen 850's idle perfectly. DSMLink allows you to adjust the global fuel settings and dead time of the injectors from stock. The PowerFC does this too. I haven't really played around with any other EMS's. Basing it off the stock injectors seems to make it a lot easier to tune.

 

[Kevin Lubitski]

My old supra had 1000cc's and it idled like stock.

 

[Lextreme II]

i want to have enough fuel to support 1200 bhp. From the formula above.

injectors size/5 x .8 x 8 = would be about 1,280 bhp

1000 cc/5 x .8 x 8 = 1,280 bhp

680 cc is the biggest size for high impedance. I will be using Woftkatz Engineering custom fuel rail for 1uzfe. I made a chart for this Injector Size and Horsepower Chart

 

[poid]

680cc should be fun to make idle.

my honda idles 680cc using altered fuel maps on the stock ECU, its not difficult.

Lex, you could always use low impedence injectors with resistors if your ECU only has high impedence injector drivers

 

[rarson]

i want to have enough fuel to support 1200 bhp. From the formula above.

injectors size/5 x .8 x 8 = would be about 1,280 bhp

1000 cc/5 x .8 x 8 = 1,280 bhp

680 cc is the biggest size for high impedance. I will be using Woftkatz Engineering custom fuel rail for 1uzfe. I made a chart for this Injector Size and Horsepower Chart

That sounds about right. I am looking at using 950cc injectors for headroom of 600 hp for my 4-cylinder.

High impedance injectors are usually easily swapped for low impedance. Does the 1UZ use a resistor pack for the high impedance injectors? If so, it should be as easy as taking that out of the wiring.

www.fuelinjectorclinic.com has very good fuel injectors for DSM's at great prices. These should fit most Japanese cars I believe, though you might have to modify the fuel rail. The best part is that right now their 950's are on sale for $340 for a set of 4. These injectors are the ball and disk type which are supposed to provide a better spray pattern than the standard pintle-style injectors.

 

[SprinterTRD]

Rarson you have it the wrong way around, high impedance injectors don't need resistor blocks.
You should not replace high impedance injectors with low ones even when you use resistor blocks on a standard ECU. The injector dead time is longer with this combo and the ECU cannot do battery compensations correctly.

On the better aftermarket ECU's you can program the correct injector current and battery comp so its not such a problem.

 

[rarson]

Whoops, you're right. Thanks for setting me straight.

I know on the RX-7 they used both high and low impedance injectors through various years (not both at the same time though). In either case, the ECU sees the same high impedance load so people generally either add or remove the resistor blocks as necessary. I've never tried changing them before, but I've heard of a lot of people that have.

I agree that an aftermarket ECU is the best way to drive any non-stock injectors. In the old days of DSM modding, people would throw oversize injectors in and "compensate" with an AFC, but even this doesn't account for the increase in dead time and thus it's hard to get the car to idle correctly.

 

[cribbj]

680 cc is the biggest size for high impedance. I will be using Woftkatz Engineering custom fuel rail for 1uzfe. I made a chart for this Injector Size and Horsepower Chart

David, 680cc isn't the biggest high impedance injector; I've got 850cc high impedance Blitz side feeds in my Supra, and I'm sure there are a few more high impedance shooters that are bigger than these.

BTW, for you low impedance P&H fans, AEM now sell a 10 channel P&H driver box, so if your ECU will only drive high impedance saturated injectors natively, or low impedance P&H injectors via a resistor box, this new P&H driver box is the thing to have, particularly if you're going with BIG squirters and you still want it to idle.

I still think two small squirters per cylinder are better than one big one, particularly if you can stage 'em.

John

 

[z8]

David

Try this site for injector calculations. www.rceng.com/technical.htm

Ernie

 

[Toysrme]

The cc/5 rule works within 99% at a stock fuel pressure. Going into the in-depth calculations isn't needed.

I would like to add, don't use 90% for a modifier when you're doing FI projects. You reall need to size duration down to 75-80% at most. Some injectors don't fuel pressure as much as others do, and if you're using a fuel pressure controller... It takes one descent spike can pin injectors sized "just right" open.
High imp injectors are made just as large as low.
Wankles came stock with 550cc primary, and 850cc secondaries. They upgrade to 1250 & 1800cc injectors all the time.


1000cc injectors would be great for 1200bhp.