exhaust mileage increase

It would have to be. Im courious as to how they dynoed the truck to get the crank h.p.

 

The engine may produce the 190 h.p. at the crank ( most manufacturers before 2006 had a -2% and a +1% error allowed ). That rating was made on a bench with the base accessories attatched to the motor. The engine looses h.p. going thru the transmission, turning the drive shaft, going thru the rear diff, and then overcomming the rotational mass of the tires. The % of loss varies depending on drive configuration ( 4x4, auto, manual, etc.) and manufacturer. I have seen the Dodge 4.7 motor ( rated at 235 h.p. ) in a 4x4 with an auto crank out 186 h.p. to the tires. Thats a 49 h.p. loss thru the drive train. Corvettes on the other hand, are much more efficient. So, its not a set number that you subtract to get the rear wheel h.p., it a %. Also, dyno results can vary from one to the other, so when doing upgrades it is very important to use the same dyno and try to match the same atmospheric conditions. As far as the Toyota Tacomas go, all the 3.4's I have dynoed have put out between 149 and 154 h.p. to the wheels when stock. The 2.7's in a 4x4 manual has put down 104 stock. The 22 h.p. gain that they say you have gained could possibly be a "mathamatical" gain, where they take the existing CFM of the new exhaust and add it to the stock CFM the engine can push @ WOT, and "compute" the increased h.p. I have see people do this, and when we have tested this methode it has proven to be pretty optomistic. Also, Torque is what get a vehicle moveing. Your 86 jimmy may very well have been putting down 100 h.p. to the tires, but Im sure it was pushing 250 lbs. of torque to get the truck moveing.

 

We were talking about the 3.4 v6. The new 4.0's are @ 200 or a little above when stco to the tires.

 

I have "genuine" information. I have spent quite a few years working on getting the most from engines. The best thing for getting more m.p.g. is your driveing style. The MOST m.p.g. increase I have seen from a Tacoma with a non stock intake, headers, and full exhaust ( that was propperly tuned, I might add ) has been 2 m.p.g. If you want the exhaust, I say get it, bump your tire psi. up a few psi, and dont change your driveing style and you wil see a couple more mpg.

 

That could very well be a possibillity.

 

The manufactures for 2007+ have to have all accessories running, full factory intake and exhaust to get the new rating. The H.p. is the same as it was in the 2006- years, just a different methode of testing. Kinda shows the loss right there of a few accesories and the like. If the manufacture meets certain criteria, they may also get the rating "certified" wich means that it puts out NO less than what it is rated at. So far, as far as I know, only GM and Toyota have given certified ratings for some of their vehicles. For GM its the Corvette, and the 5.3 and 6.0 truck motors. Toyota has certified the 4.0 in the Tacoma and the FJ last I heard.

 

Without seeing your setup its hard to make a guess. You went with a larger muffler ( a good thing ) and went with larger 3" pipes ( not such a good thing on these motors ). I think you may have gained a good amount of torque on the mid to top end, but I would think ( one again without seeing your setup ) you may have lost some on the bottom. I have ran a couple of 3.4's on a dyno with a similar exhaust as you have, i.e; daul pipes and a bigger muffler, and that has been the norm. It still gives a performance increase as the truck is now pulling a little harder in the mid to top end, and if you have good gearing, you may not feel any loss on the bottom.

 

LOL. I know the feeling. My wife keeps mine in her purse. I take them out when she's not looking.

 

True. Just stay away from the "baffled" mufflers( Flowmaster ), as they actually give a loss on these trucks. They sound cool, though.