LostInSpace

As we get tantalisingly close to delivery of the 32V performance cam group buy organised by Colin, I'm starting to think about higher flow injectors to support the increased breathing.

Have a look here for info on the Cams, finalised spec's are on the last page or so:

http://www.reutterwerk.com/forums/sh...ad.php?t=12927

The cam's are going into a 1990 GT, which currently has a set of Bosch manufactured 'Ford Motorsport' 19lb injectors. General consensus is 19's are near capacity therefore an upgrade is required. Question is, upgrade to what?

24lb/hr would be a minimum, perhaps something like these Bosch 0280150947/0280150965 from Five0: http://www.fiveomotorsport.com/product-search/?v=23333

Particularly interested in what others in the cam group buy will be doing and welcome info from any of the tuning guru's amongst us.

123quattro

How much power do you want to make?

Roughly speaking...

injector flow rate (lb/hr) x number of cylinders x 2 = crank hp

jleidel

LostInSpace, take a look at the various Ford Motorsport 24lb injectors. The latest revisions have a more aggressive spray pattern. [also check Blue Oval Motorsports, they generally have good prices on Bosch injectors].

I've seen larger Bosch-type injectors for Ford applications, but I'm not sure of the fit on a 928...

Speedtoys

What cams there?

LostInSpace

Well, you can never have enough power

So taking the formula we get:

Stock 19's we get 19 x 8 x 2 = 304

24's = 24 x 8 x 2 = 384
30's = 30 x 8 x 2 = 480

Obviously, you can't just throw in really big injectors, they need to be sized to the volume of air being supplied.

Other upgrades will be a motorsport 2.5" X-Pipe and full mandrel bent 2.5" exhaust and Sharktuning. Stock exhaust manifolds.

I'm realistically hoping for an approx 50hp increase, so somewhere in the region of 380-400 Crank HP, which is at the upper end of the 24's range. 30's will comfortably handle the HP, however I don't know how they would behave around idle, would the duty cycle be too short leading to rough idle?

What are other people with performance NA motors running? What's the duty cycle like on 24's at WOT/high RPM?

Hilton

He meant this thread/post:

http://reutterwerk.com/forums/showpo...&postcount=167

LostInSpace

Link edited to the Cam thread.... Dooooooh!

Lizard928

You also have to keep in mind that the injectors are being run at a higher pressure, therefor supporting more power.

IIRC the 24# injectors are good for around 400WHP. On the S4, but I could be wrong on that.

I am planning on adding some boost shortly after the cams (one can never have enough power), so I will be installing a set of 60# siemens high impedance injectors at the same time as installing the cams. Unless I find a good deal on a set of 42# injectors between now and then.....

Imo000

50hp out of a set of cams and an X-pipe? Isn't that a little optimistic?

hacker-pschorr

Based on what?
Cam & Exhaust on other V8's can gain a hell of a lot more than 50hp.

On one extreme in a Vette that already had exhaust mods, an 80+hp gain isn't unheard of:

http://forums.corvetteforum.com/c6-t...am-in-ls2.html


Here's a C5, from what I've seen the under-drive pulleys are good for 8-10 hp meaning the cam alone was good for 60hp:

http://forums.corvetteforum.com/c5-t...-g5xe-cam.html


GTO with stock heads = 50rwhp gain from the cam:

http://www.ls1tech.com/forums/dynamo...y-new-cam.html

Speedtoys

No way, on a Honda, its closer to 75. (If you use the included stickers)

Lizard928

I dont think that 50BHP is overly optimistic.

When you look at how restrictive the stock cams are, and how good the heads really are.
Although I will soon prove or disprove that.

jcorenman

Data point: Sue's GT with headers, x-pipe and 2.5" dual exhaust, otherwise stock, is 346 rwhp. (That's like 75hp on me, plus a lower rear end, it's embarassing). Injectors are 24# 4-hole Ford/Bosch injectors, no half-rate injection (threshold moved above redline), max pulse-width is around 8.2 ms at 6500 rpm with AFR ariound 13:1.

Normally (for an S4/GT/GTS) the injectors fire once per revolution up to 5100, and then every second revolution. The reason is that it takes time to open the injectors (0.94ms is what the LH uses as opening-time), and cycling half as fast means less time lost to overhead.

With 24# injectors the injector pulse-width (open-time) is shorter, and the opening-time for newer injectors is quicker-- 0.85ms. So firing once per revolution all the way to redline is fine. I am not sure that it buys any horsepower, but seems more sensible.

And most folks recommend a max injector duty-cycle of around 80%, they need some off-time. The 8.2ms I quoted above is the number from the ST2, which includes the opening time. So the real open-time is approx 7.3ms, and at 6500 RPM that works out to 79% duty cycle.

If you are looking at max HP for a given injector, that is probably at 100% duty-cycle at spec'ed pressure which is less than our stock pressure. So add HP for higher pressure, deduct for 80% max duty cycle, probably a wash. But it also looks like our 346 is close to the max for 24# (without half-cycling).

LostInSpace

Colin,

I very much hope you disprove that as well

I didn't want to get into adding up the HP gains for individual components as we all know it doesn't work like that in the real world, which is why the projections are conservative.

LostInSpace

Jim - thanks for the info and what I was looking for. A quick Google found several online injector sizing tools and they all referenced 80% as max duty cycle.

I've asked for detailed tech specs on both the 24's and 30's from Five O and will post info this evening.