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Casper said:
it's a full pi motor with pi intake, 2.5 true dual setup.

Thats what I was thinking, its a stock motor with stock exhaust manifolds. The stock MN12 exhaust manifolds don't flow as well as stock Mustang ones, the car is alot heavier, and first gear is not as deep as what is in a 5 speed. IMHO its a big cam for his combo and he would run just as fast if not faster with a cam one step smaller.
 

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Silenced said:
Why?

Gears aren't going to effect the power output or powercurve of the engine. It will put you in a different spot on the powercurve after shifts, but being a stock motor, and him probably not wanting to rev it over 6000rpms, that limits him to 4.10s at a maximum. there is a 10% difference between 4.10s, and 3.73s. If he is interested in still getting good highway mileage, there is absolutely nothing wrong with that.

As for compression, yes, it would make more power, but does he need it? No. Warlockguitarman put out (Note: I cannot attest to the accuracy of the Dyno's calibration) 279hp with these cams on a pi headswap'd engine with the powercurve starting around 4000 and ending at a little higher than 6000rpms. If you lower the compression, you will loose power the entire powerband, but the characteristics of the curve won't change enough to need to switch pistons....

He might need more than 3500 stall, but thats his prefrence, and its not a requirement. Once again, it all depends on his goal for this car.


Steeper gears make the car easier to move (leverage), thats why many times you see gas mileage increases in the city with them.

With the automatic gear spread of the 4R70W if he shifts at 6000RPM in first gear he will drop way down to about 3300RPM in 2nd, and the 6000RPM shift at 2nd will drop him down to ~3900RPM in 3rd. This is the problem with big cams on these heavy 4R70W cars, you will spend more time on the bottom of the power curve compared to a 5 speed Mustang.

If he is not wanting to shift at 6000 then that cam is definately too big, thats all there is to that.

Bigger cams have more overlap so they will bleed more dynamic cylinder pressure at lower RPM. The engine is more spark tolerant at higher RPMs due to the faster swirl in the chamber/cylinder. Bigger cams work hand in hand with higher compression. Something else not well known unless you have spent alot of time behind a dyno, the higher the compression the less the exhaust flow matters, which is a big plus for these cars. And the best part of all - these 4.6 motors will handle a ton more compression than other motors and run fine on pump gas.

279RWHP peak is cool, what does the curve look like is actually what I would care about.
 

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Refrigerator Raider Hater
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You do realize that cam is milder than a 262ah? It doesn't even have any overlap @0.050" lift.
 

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Fry Rice Specialist
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Discussion Starter · #24 ·
well decided on the crower stage 2 because of so many recommendations from many other and not heard any horror stories yet about it. the power range on this cam is 1250-6000+ so i'm pretyy good with it. comps 262ah sounds good also but read couple stories with issues about quality so i'm gonna stay away from comps.

fuel compsumption is not a big deal with me becausse my car is only averaging 16-18 mpg now with npi high mileage stock motor. figure out with new pi explorer i'll pick up considerable amount of mpg then from there it drop a little bit after cam i still don't mind. just didn't want 12-14 mpg and i'm fine wiith it.

what is the difference between sc and na cam? what's gonna happen if i use sc cam instead of na stage 2 cam in na engine?
 

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Casper said:
fuel compsumption is not a big deal with me becausse my car is only averaging 16-18 mpg now with npi high mileage stock motor. figure out with new pi explorer i'll pick up considerable amount of mpg then from there it drop a little bit after cam i still don't mind. just didn't want 12-14 mpg and i'm fine wiith it.
well think again partner, because you might end up where you dont want to be at in fuel economy......if you think the PI motor will bump you up to 22mpg, and then the cams will bump it back down to 16-18 mpg once again, i'd have to say you're wrong......especially with those cams

when i was still runing with the stock NPI motor, i would average bout 17 mpg city.....then i went with PI heads and some Crower Cams (222* @ 0.50", 112 LSA, 0.49" lift), and 12-14 mpg is exactly where i'm at now.......and remember its a milder cam than the one you're getting........i can top 27 mpg on the hwy, but in city driving, the tall gears and low stall converter keep cams spinning too low and wind up slow.........why did it drop so low?........ like it was mentioned, the larger overlap bleeds off cylinder pressure, and the larger duration also kills some torque down low......this coupled with a stock 3.27 gear and marauder converter, keep the engine too long in the low rpm in city driving......once i go with steeper gears (4.30-4.56) and a higher stall, then i expect somewhat of an increase in city mpg

keep your fingers crossed buddy, but at the same time, expect the worst lol
 

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Fry Rice Specialist
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Discussion Starter · #26 ·
then i'm sol now huh? lol...

guess now is go big or go home...:D
 

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Casper said:
what is the difference between sc and na cam? what's gonna happen if i use sc cam instead of na stage 2 cam in na engine?
Blower cams usually sport more intake duration, and increased overlap. Different manufactures cam specs will vary, but generally the additional duration allows the valve event to remain open longer in order to increase the engines ability to fill the cylinder and fuel the intake charge. Increased overlap will lower your dynamic compression ratio controlling the length of time both the intake and exhaust valve are open simultaneously in order to bleeding off some of the compression.....which allows you to run a little more timing under boost. Great for a blower car, not exactly ideal for a N/A engine....especially one running stock compression!
 

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Casper said:
then i'm sol now huh? lol...

guess now is go big or go home...:D
you'll be fine with what you selected.
 

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Casper said:
then i'm sol now huh? lol...

guess now is go big or go home...:D

its not that you're necessarily sol, just gotta remember that everything needs to be optimized accordingly: gearing, converter stall, timing/tune, shift points, converter lock/unlock schedules, etc, etc....get everything right on the money, and you could very well be 16+ mpg like before, as i am expecting to be once everything falls into place
 
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