87RXGhey7

WWWWWWWWWWWWWelllllllllll, I took my car to the dyno and got 113.9 horse and 111.8 torque on 90 octane gas. My air/fuel ratios were messed, I think, they were 13.8 all the way through except around 3.8k rpm where all of the sudden it got really lean, and my horsepower/torque dropped off, but then came back up. I was wondering if 14.7 air/fuel ratio was the number to shoot for, or wtf? I kept thinking 11.9 was the number to shoot for, but on my way home, it hit me that that is a good number to shoot for if I had a turbo. Thanks, have a good day.

Ronac

Is that an average number for a n/a fc? Is it just me of does 113.9 seem low? what mod's do you have in your car?

bingoboy

mmm not too bad for an s4. no mods on the car yet?

maybe your aux ports are sticking and not opening when they should, thus the dip in power in the middle.

as for getting really lean...if you weren't detonating there is no reason it should have lost power. if you don't detonate, leaner is better. my a/f ran at about 12:1 from 5-7k and then went to 10:1 by 8k which is super rich. i hear for an NA you want it around 13 to 13.5. i would have gotten more power at it leaned out a bit. 11.9 is rich for an NA, you're right thats more of a turbo number.

do you have the sheet you could scan in to show us? that would help if you want to know about your a/f readings etc.

bingoboy

they told me when i dyno'd my car that a series 5 NA would see approx 124 at the wheels in their experience. if so then 113.9 for a series 4 seems to be right on the money since they are like 15 hp less.

kllntyme

That seems like the driveline is really parasitic on these cars. It sure as hell doesn't feel like that many of my ponies are being rotated away.

kllntyme

Also I used to have a power drop at 3800. One of my ports wasn't opening at all. I always wondered why my poor rex had a constant carbon issue.

bingoboy

on my dyno graph of the torque it was reall easy to see where the ports and vdi kicked in. torque would start to drop and then pop back up.

87RXGhey7

no cats and cold air. Seems low to me, but Im not real sure.

bingoboy

yeah it does seem a titch low. how many miles on the engine?

skydivr73

btw guys--there are several issues that can cause that power drop at 3800.....a common one is grounding--if you ground your engine better in different places, it can get rid of that. Also--if he is leaning out, then it wouldn't be a stuck port--he is getting LESS fuel and MORE air, not LESS air. If your aux port was stuck then you would be getting less air. Do a search for the 3800 hesitation. Keep in mind that this is when the secondary injectors are supposed to come online, so if you're getting lean, then I would look there first.

Slammedblk7

iTrader: (7)

ah, dont feel bad, i made a measly 127hp and 125lb/ft of torque that was before i fixed my VDI problem...she should be well past that now.

Z3r0

I did mine and got 117 hp and 98 tq, I have intake and no cats as well.

1987RX7guy

iTrader: (3)

given you don't have cats I will assume you have just a race pipe. If this is correct your auxilary ports don't work meaning you loose al the top end HP that they give you.

bingoboy

good call on that, how could that have slipped my mind. with no cats on a Series 4 car, you will need to wire the ports open or get a racing beat presilencer with the tube for the backpressure. my buddy has no cats, the presilencer and an exhaust on his S4 NA FC and the ports still open with that setup. you might look into that.

ilike2eatricers

87rxghey7 why were you running 90 octane? Safety precaution against detonation. If so I guess I understand but running higher than 87 octane on a na fc could hurt your performance unless your car was tuned for higher octane.

1987RX7guy

iTrader: (3)

I also wanted to mention that.

87RXGhey7

I have stock cat back, so the ports should be opening.

1987RX7guy

iTrader: (3)

There is no evidence that I have seen so far that supports your belief. Unless there is 4 PSI in the exhaust system and you hooke the split air tube back up to the exhaust somehow. They are NOT opening. Did you have the split air tube put on the race pipe?

Also given you have no cats meaning a race pipe you should have a nice HP increase. Your dyno numbers are pathetic even for an N/a in stock condition.


*EDIT* I just ran those numbers and according to the stock BHP of the S4 engine which is 146 and your dyno numbers you have a 22% power train loss of HP.

Kim

I made 161fwhp and 143 rwhp with no emissions, ps or ac the 5/6th port BUTTERFLIES works and i have a header and resonators, K&N in homemade coldairbox.
Ive marked the line because the original printout sucked bigtime...And yes I know the HP line is kindda wrong but the marking isnt superexactly(got a little far)


Torque is in NewtonMeters which is metric I have no clue how to get it into PoundsSquareFoot...

bingoboy

how did you measure flywheel hp Kim?

pillage6

You should be using the lowest octane rating you can for n/a.

The opposite is true for turbo cars.

87RXGhey7

why use the lowest octane?

My88Se

iTrader: (10)

Because higher octane is just to help prevent detonation. Unless you've done some crazy tinkering with the timing, that shouldn't be a problem on your NA.
Just use the lowest octane you can find, it'll make your car run better.

hypntyz7

Octane, contrary to popular belief, is not a measure of power output, but a measure of volatility, or resistance to detonation. Detonation (ping, preignition) occurs because fuel burns too quickly/wildly for the engine/conditions. Lower octane burns faster, produces more power, but is more likely to ping. IN a nonturbo, conditions are nowhere near favorable for detonation, so the lowest octane you can find will produce the most power.

IN a turbo, supercharged, or high compression nonturbo engine (10:1 or higher), you commonly see higher octane requirements because of the setup and nature of the engine. They make much more power than a normal nonturbo engine, but they only hold together because of higher octane use. IF they used lower octane in such an engine, the power output would go even farther up, but the engine wouldnt hold together long.

This is why the notion of putting race gas into a honda or other lightly modified street car is so silly. You have kids that spend $50 on a tankful of 100-110 octane race gas to give their car the edge on the street. In reality they've just made it slower, because the higher octane gives less power output. IT is only if you have a high power engine setup prone to detonation that you need the high octane to stay safe and still make good power.

Kim

I really dont know but the guy who did the dyno run said that this is what it had on the motor and rear wheel hp was 142.something.
It was just a fun run as i didnt adjust anything.
My buddy OC94RX7 had a schedueled time on the dyno that day, and we figured it would be fun to test mine too.
And i got surprised that it did have that much on the rear wheels, I was guessing 130ish