HTX

iTrader: (1)

hey guys i have 02Z28 with fullbotons, kooks headers, 3.73's and soon to come VIG 3800 or 4c converter. the only thing stopping me from putting a donkey dick cam is fuel economy. (please do not chime in with a ******* "shoulda bought a honda" comment. you are not helping) i was hoping you guys could help me out with this part. I currently get 15/20 mpg and really dont want to loose more than 2-5 mpg. with the converter i am going with i have little interest in lowend power. i care more bout top end and roll racing i want my power in the 4000 - 6500 rpm range. i was looking into an XFI lobe on a 230/230+ 112 duration.

with my being aware of fuel economy should i go with a 224 XFI and extend the exhaust durationt to 230+on the XER profile?

is there a huge difference in a 224 cam and a larger cam with fuel economy?

my goals are to put down at least 380rwhp and mid 11's full weight and 275 DR's.

Thanks guys.

BYE RICE

iTrader: (2)

Shoulda bought a six speed?

Your doing it backwards..Match the stall speed to the desired cam..not the other way around.
Once you make up your mind, it's going to come down to the quality of the tune ,including getting the converter in lock-up quickly.
The only other thing I could think of would be to go with 3.42's.

I get 26 mpg highway with a 236/242 111 lsa cam.

HTX

iTrader: (1)

lol shoulda bought a 6 speed but i didnt. and even if i stick with stock i would be getting a large stall anyways. I had a VIG3200 on my other camaro and it wasnt enough, but of course i may have to go smaller seeing as though i may be asking for too much.

im assuming you are a 6 speed?

by the way. how is LSA Anaconda goin for yah?

BYE RICE

iTrader: (2)

Balad is DUSTY..I havent seen the sun directly in two days.
Yeah..I rock a six speed.
You say your emphasis is roll racing..
Even more reason for a six speed...
An auto shines on the drag strip/from a dig.
P/M Patrick G on this forum & he'll sort your combo out for you.
He spec'd my cam..It'll cost you a few bucks,but it's money well spent.
Where you located?

HTX

iTrader: (1)

im in Mosul left ballad back in September. I miss Med Red days. They dont even have Medivac in Mosul.

home is Houston

Sid447

If you want to keep economy,

Keep an eye on your valve overlap @ 0.050"

Camshaft overlap @ 0.50” = ((intake duration + exhaust duration) / 4 - LSA) x 2.

e.g. 220/224cam with a 110LSA
1] 220+224 = 444 / 4 = 111
2] 111 -110 = +1 ( One degree of overlap here at 0.050")

e.g.2 212/218 on a 112LSA

1] 212+218 = 430 / 4 = 107.5
2] 107.5 -112 = -4.5 ( no overlap @ 0.050").

The further you go into PLUS! figures, regardless of cam, the bigger the impact on economy.
Regardless of the tune. It's basic law of physics.

HTX

iTrader: (1)

ok good info. thank you. a lower LSA will help improve economy even though the rougher idle? i think i see error in your math with the second example. 113-112 = -1?
why is that negetive? or just simple error? if its not an error i dont think understand.

so 230 230 112
230+230=460
460\4 = 115
115 - 112 = +3

so by that math it appears a 230230 112 would be better fuel economy than the 220224 listed above.

Sid447

I've never seen,

a validated test to show BSFC's or real world economy comparison between say a stock LS1 cam (which has a 116.5* to about a 119.5* LSA) and compared it with another small stick with a tighter LSA.

(That's not to say there aren't any, I've never searched intently).

I'm sure some cam companies have a real good idea on what would work & how to improve the economy quite easily as the wide LSA we got with Gen 3's was to satisfy California idle emissions I believe.

It's something that no doubt, would be considered these days with the cost of fuel rocketing.

HTX

iTrader: (1)

i think maybe the positive overlap numbers would be reponsible for the loss of fuel economy as opposed to negetive overlap.

01ssreda4

iTrader: (96)

hp seems like a very reasonable goal but going mid 11's on a 275 DR is gonna be kinda hard if you ask me. that stall your talking about is gonna give the DRs hell off the line.

Sid447

HTX,

Sorry,

At least your logic was working...

I must have had my head in the sand

The basic calculation is correct.

However when you end up with a +figure the cam has overlap
The way I had it a stocker would have more overlap than your 230/230 example.

HTX

iTrader: (1)

well my car puts down only 325/340 with current setup but it runs a 12.4 (i have full suspension - a torque arm)

so... with cam and stall i would hope to achieve a 11.8 but i like to set my goals high

well one guy just pmed me nd said his 230 cam w/ 4000 stall still gets 18mpg highway. I would be happy with that. only thing is he has ramair

Patrick G

iTrader: (14)

There is sooooo much fuel economy to be gained by just getting a razor sharp VE and drivability tune. With tuning, you can make your cold starts perfect. You can optimize your timing tables at cruising rpm. You can even lock up your converter early to pick up some mpg. I have successfully gotten excellent fuel economy with cams larger than the 230/230 112LSA of the OP. The key was with the tune. If you can't do this yourself, be sure to find somebody who can.

HTX

iTrader: (1)

ok. but what do you mean by razor sharp VE?

damn now i really feel like a dumbass

i wont be doing the tuning. most likeley it will be LMR or Pavlock.

Patrick G

iTrader: (14)

Razor sharp means that at every load cell below 90 KPa and all rpm below 4000, your air fuel ratio is an exact 14.7:1. To do this, your VE tables will have to be adjusted. A half-*** job will not give you the fuel economy benefits we're talking about. If your MAF is not stock, then your MAF will most likely need to be rescaled too. Ideally, your Long and Short term fuel trims should be 0 all the time.