sdpatt
Sr. SHO Engr.
I had the old girl (268,400 miles) on the dyno Saturday (Dec 7th) to check her relative health and the effects of the different sample tubes on the Vortech 73mm MAF. The sample tubes were the 24 lb/hr tube originally equipped with the MAF sensor body and the 19 lb/hr Mustang-calibrated sample tube.
The dyno tests were successive and conducted without any aftermarket EPROM chips in the EEC. The comparison was an excellent demonstration of the changes that can be made with just the signal differences from the the mass air flow sensor since the actual air flow through the sensor was not affected.
My well seasoned engine is still generating 192.8 hp at the wheels (232.3 at the crank) on a relatively flat peak from about 5,700 rpm to 6,200 rpm. The power dropped off only slightly above the 6,200 rpm power peak to 178 hp (214.5) at 7,000 rpm. The torque figure peaked at 190.1 lb-ft (229.0 at the crank) at 4,200 rpm and was above 180 lb-ft (216.8) from 4,000 to 5,700 rpm. So my engine is still generating 5.6% more horsepower and 14.5% more lb-ft of torque than the ratings for a new SHO engine (220 hp and 200 lb-ft).
At 3,000 rpm, the lowest engine speed tested at full throttle, there was a gain of 12 hp and 20 lb/ft with the Mustang sample tube. By 3,500 rpm the difference was reduced to about 8 hp and 12 lb/ft. After the secondaries opened at 3,950 rpm, the difference held fairly constant at about 5 hp and 5 lb/ft.
The information I have read before indicated that the 73mm sensor body with the SHO injector-specific 24 lb/hr sample tube tended to run the SHO on the lean side. This was confirmed as the air:fuel ratio was as lean as 15.5:1 in the 3,000 - 3,500 rpm range and between 14.7:1 and 15.0:1 in the 3,500 - 5,500 rpm range. Beyond 5,500 rpm, the ratio dropped to a fairly constant 14.0:1.
With the Mustang's sample tube calibrated for 19 lb/hr injectors, the air:fuel ratio was kept very close to the stoichiometrically correct 14.7:1 up to 5,000 rpm and richened above that figure to about 12.5:1 at 7,000 rpm.
For those that have tested the engine's output with different chip calibrations, I would care to hear how these fuel curves compare to those that generated the best output. All of the other SHOs generated air:fuel curves that were significantly richer than those drawn by my engine.
Engine Output, 73mm MAF, 19 (Mustang) & 24 lb/hr (SHO) Sample Tubes
Horsepower @ rpm x 1000
SaT__3.0__3.5___4.0__4.5___5.0__5.5___6.0__6.5___7.0
19:__103__115__138__158__165__187__193__190__178
24:__090__108__125__153__160__184__190__187__N/A
Torque @ rpm x 1000
SaT__3.0__3.5___4.0__4.5___5.0__5.5___6.0__6.5___7.0
19:__182__172__182__185__180__180__167__155__132
24:__158__160__173__181__175__175__165__151__N/A
A picture is worth a thousand words...
<small>[ December 09, 2002, 11:31 PM: Message edited by: sdpatt ]</small>
The dyno tests were successive and conducted without any aftermarket EPROM chips in the EEC. The comparison was an excellent demonstration of the changes that can be made with just the signal differences from the the mass air flow sensor since the actual air flow through the sensor was not affected.
My well seasoned engine is still generating 192.8 hp at the wheels (232.3 at the crank) on a relatively flat peak from about 5,700 rpm to 6,200 rpm. The power dropped off only slightly above the 6,200 rpm power peak to 178 hp (214.5) at 7,000 rpm. The torque figure peaked at 190.1 lb-ft (229.0 at the crank) at 4,200 rpm and was above 180 lb-ft (216.8) from 4,000 to 5,700 rpm. So my engine is still generating 5.6% more horsepower and 14.5% more lb-ft of torque than the ratings for a new SHO engine (220 hp and 200 lb-ft).
At 3,000 rpm, the lowest engine speed tested at full throttle, there was a gain of 12 hp and 20 lb/ft with the Mustang sample tube. By 3,500 rpm the difference was reduced to about 8 hp and 12 lb/ft. After the secondaries opened at 3,950 rpm, the difference held fairly constant at about 5 hp and 5 lb/ft.
The information I have read before indicated that the 73mm sensor body with the SHO injector-specific 24 lb/hr sample tube tended to run the SHO on the lean side. This was confirmed as the air:fuel ratio was as lean as 15.5:1 in the 3,000 - 3,500 rpm range and between 14.7:1 and 15.0:1 in the 3,500 - 5,500 rpm range. Beyond 5,500 rpm, the ratio dropped to a fairly constant 14.0:1.
With the Mustang's sample tube calibrated for 19 lb/hr injectors, the air:fuel ratio was kept very close to the stoichiometrically correct 14.7:1 up to 5,000 rpm and richened above that figure to about 12.5:1 at 7,000 rpm.
For those that have tested the engine's output with different chip calibrations, I would care to hear how these fuel curves compare to those that generated the best output. All of the other SHOs generated air:fuel curves that were significantly richer than those drawn by my engine.
Engine Output, 73mm MAF, 19 (Mustang) & 24 lb/hr (SHO) Sample Tubes
Horsepower @ rpm x 1000
SaT__3.0__3.5___4.0__4.5___5.0__5.5___6.0__6.5___7.0
19:__103__115__138__158__165__187__193__190__178
24:__090__108__125__153__160__184__190__187__N/A
Torque @ rpm x 1000
SaT__3.0__3.5___4.0__4.5___5.0__5.5___6.0__6.5___7.0
19:__182__172__182__185__180__180__167__155__132
24:__158__160__173__181__175__175__165__151__N/A
A picture is worth a thousand words...
<small>[ December 09, 2002, 11:31 PM: Message edited by: sdpatt ]</small>
His torque curve was also very impressive, partially due to his correct air/fuel mix. OH Scott has one **** of a nice handling/braking SHO. I just want to see his and Tony's readouts again. (tony had like 355@ the tires)with like 15psi. thumbs_u Thanx to all the great Lone Star guys. Craig
