Tony Mamo @ AFR

iTrader: (13)

Guys...

I have been wanting to step in this thread quickly for some time now (been sidetracked with my 383 project). While I don't have any cut and dry answers or magical solutions to Pat's results (which are a little puzzling), I'm confident this guy will find more because he is one of the most determined enthusiasts I've run into on this board and others...at least I certainly hope he finds more because I'm sure there will be a tremendous effort put forth to do so.

My thoughts are due to the fact the engine leaned out with the larger, higher flowing heads (based on his fixed previous 205 speed density calculations), it confirms that the engine is in fact ingesting some of that extra air available with the higher peak flow the 225 heads brought to the table. Considering the chamber design is the same, the same frictional losses in the engine, cam timing, compression, etc....it would have been logical that when Pat added extra fuel to bring the A/F ratios more in line, there would be more energy available to produce more power (more than 5 HP based on fueling and estimated additional air intake).

On the other side of the equation, is the manifold restricting some of the upper lift gains in airflow....I would say certainly some of the bigger gains have been lopped off by the intake (even a ported FAST is still somewhat limited in it's abilities). But once again, if thats true, why did the engine seem to have an appetite for additional fuel???

Im hoping with more time spent on the dyno and tweaking of the fuel and spark tables Pat could perhaps dig up another 5 or so putting him solidly 10 better than his previous combo (and no loss of bottom @ WOT), but based on airflow increases was really hoping for something closer to 12-15 going in to this experiment. It certainly reinforces the fact that an efficient, high flowing 205 cc head is hard to beat for a good strong running dual purpose car, and certainly gets the nod for anyone really wanting to place an emphasis on low speed part throttle response and fuel economy. While the WOT at low RPM might not show any losses, there will still be a loss of throttle response and "snap" with the larger cylinder at low speed part throttle conditions where the airspeed will be more greatly affected by volume and cross section.

I look foward to Pat's additional results, continued testing, perhaps some answers and hopefully some additional power. I know for a fact Pat didn't have enough time the day he spent on the dyno to really wring out the new combo....perhaps a little extra time is all he needs.



Tony M.

DAPSUPRSLO

iTrader: (14)

Sounds to me like he just needs more time to work out all of the ve tuning with the combo too! Gollum throws in some good ideas as well with the possible air/fuel separation issues. Only time and further testing will show.

Patrick G

iTrader: (14)

I doubt it's a fuel separation issue only because we're working with too many known variables.

1. The AFR 225 small bore heads use the proven dual quench pad combustion chamber found on the AFR 205 heads. Flame travel, quench and squish should be identical between heads.

2. The AFR 225 small bore heads use the proven port design from the large bore 225s. These heads have proven themselves time and again to make big power in all applications. The runner design is sound.

If there were a fuel separation issue, the power would have been down and not up. I just need to continue refining the tune. FWIW, we gained 20 rwhp/rwtq by leaning the mixture from 12.4 to 13.8. The more we leaned it out, the more power it made. I think with a little more leaning out and a timing adjustment, we'll be on the money with our increased power.

Timing is the biggest wild card. I wouldn't be surprised if we actually picked up power by retarding the timing some. Currently, we're at 26 degrees for peak torque, and 29 degrees at peak power. I might try more timing at peak torque and less timing at peak power. I'll try everything to maximize the setup. Anyone have any thoughts on timing? Keep in mind, I'm running a really tight quench (.032").

WS6FirebirdTA00

iTrader: (33)

i would try to drop the timing 2-3* across the board, i went from 29-31 on my car down to 25-28 depending on rpm and saw biggest changes, and felt them. no dyno but i had more wheel spin in 2nd gear and i saw more manifold vacuum and higher dynamic airflow. so you are running about 13.8:1 AFR?

Patrick G

iTrader: (14)

Yes, according to the probe you stick up the exhaust, I'm running 13.8:1 AFR, but I've never trusted those things to be totally accurate...not like a wideband in a closed exhaust. Those Dynojet probes always seem to read a little on the lean side. I bet my A/F ratio is closer to 13.0 in reality. I'll probably pick up power by leaning it a little more. Then timing.

For cruise timing, I'll set my cruise control, then use my bi-directional controls in EFI Live to vary timing while at speed. By monitoring throttle position, I'll set my cruise timing to give me the most speed with the smallest TPS%. I'll need a long stretch of level road to do it, but along the Texas coast, that should be no problem (no hills).

WS6FirebirdTA00

iTrader: (33)

when do you plan on getting it back on the dyno? and what injectors are you running with that kinda power?

zo6vetteman2003

iTrader: (1)

Are you running stock injectors? Your flow almost sounds like you are running a saturated circuit driver type fuel injector and it cannot react fast enough as the peak and hold type injector.

WS6FirebirdTA00

iTrader: (33)

ok 37# injectors i see, i would think that would be enough but just curious, what duty cycle are you seeing, or pulse width WOT

WS6FirebirdTA00

iTrader: (33)

nvm they should support ~525 rwhp at 80%

Patrick G

iTrader: (14)

I haven't checked injector pulse width in a while, but I remember it was in the 70% range with my Racetronix injectors. Those 37lb injectors flow around 43lbs at 3 bar. Also, don't forget, I have the Racetronix fuel system so I have plenty of pump too.

WS6FirebirdTA00

iTrader: (33)

do you have a scan of that last dyno run you had?

Patrick G

iTrader: (14)

No, unfortunately the printer at Thunder was broken. I'll try to see if they can e-mail me the files.

WS6FirebirdTA00

iTrader: (33)

did you hook live to and log data for the run or no? just wonder if you can compair scan data from old to new

Patrick G

iTrader: (14)

I have lots of WOT runs logged with the 205 and the 225s. My dynamic airflow was in the high 350s with the 205s and with the 225s it's in the high 260s to low 370s. Of course, this is subject to change somewhat with more leaning, but right now, my A/F ratio with the 225s is exactly the same as when the 205s made the most power.

WS6FirebirdTA00

iTrader: (33)

what rpm did you see that airflow value at? just curious how it compairs to mine. also what afr did the 205's make the most power?

thats a pretty big increase in airflow. gotta wonder if it was just the dyno? a guy on here went to 225 heads and lost power but ran his fastest track times, kinda odd but who cares if you are fast!

Patrick G

iTrader: (14)

About 6500 rpm is where I made those numbers. AFRs made best power with narrow band sensors at .890-.900mv, which coincided to 13.8:1 A/F ratio on the chassis dyno with the DJ probe up the cutout. Reality is the A/F ratio was probably closer to 13.0:1. With narrow band tuning, the A/F ratio was perfectly flat when we dynoed the 205s. The A/F ratio was not near as flat with the 225s.

If I go off of SOTP, my car feels quite a bit faster...especially in the mid-range.

Rick@Synergy

iTrader: (5)

I seem to be late int he post, but maybe my view can help out....Here is how I see it.

The 205 wants more fuel down low due to runner length and air speed. More air able to flow down low according to AFR's head design. So more VE. Now up top, the runner length is alot bigger so its already willing to fill the cylinder alot more, so now your VE is going to be higher. IF I were you, more Air should mean less timing. Try going down a few degrees on TQ peak, and at the same time add fuel. If you drop timing, you need fuel to back it. If you add timing, less fuel is needed. Sound weird, but it works. But every car is different.

Does your VE graph follow your TQ graph? If not, then you are missing something or your power is not matching up the way it should. Keep an eye on this.

Rick

zo6vetteman2003

iTrader: (1)

Sounds like been there done that......

98Aggie

iTrader: (19)

Hey Patrick, looks like I will be moving the mustang Dyno into my shop, sometime in the next week or so. Give me a call sometime.

Also I should have my car finished soon, been waiting on the fuel pump.
Kurt

ninobrn99

iTrader: (8)

btw pat, any new results?