The car lit up the CEL last night. I brought it in to the dealer today and they pulled the codes P0301 - Misfire Cylinder #1, P0420 - Catalyst System Efficiency Below Threshold, P0503 Speed Sensor Intermittent/Erratic/High.

We flushed the codes and started the car again and only P0301 came up. The fix was to replace the coil ignition and all the spark plugs (to iridium). The car is now butter smooth and idles smoother than ever.

Could a weak ignition coil and the wrong spark plugs have lowered the dyno readings? I didn't have a CEL at the time of the runs which was a week and a half ago.

 

i would think it could... not running irridium will lower ur dyno results by itself... run another dyno run if u can...

i would like to see what ur numbers are... im still trying to look for a cheap used auto S/C to add with my nitrous

 

I just looked up the iridium spark plug they put in 90080-91180 Denso SK20R11. This is the wrong plug for the supercharged tC. The TRD spec is to use a copper Denso K22PR-U gapped to .032". The SK20R11 is the OE plug with a .044" gap. *doh* There is even a sticker in the engine bay telling them the right part numbers.

I'll wait for the weather to cool down before another dyno run. It's been really hot lately and I want to run it in similar conditions to the first run for comparison reasons.

 

did u ever get another dyno done?

 

X2! Stock auto's dyno 120-130 range so that seems right.

 

I spoke with the dyno owner and he didn't think it would be worth my money to do another (each session is like $90). The failing coils and dead cat would probably affect a few HP but together they would NOT have made a large enough change to be worth it. Consolation was that I was probably hitting 215hp at the crank which is in the right ball park as the folks with similar setups hitting 190WHP on their manuals. Its sad but the auto tranny with it's torque converter probably does eat up at least 20WHP.

I'm looking on the bright side that it's still a good ride. It's not the fastest but quick enough to be enjoyable.

 

well, with all that fixed, if the car makes more power, it should be noticible from the seat.

man, so glad i have a manual...

 

I'm getting better mileage I can feel that from the wallet. All I've been driving is rush hour so there's no way I can tell the different between +10hp and nothing.

 

Spark plug type won't effect hp drasticlly or any at all if they are fresh and have the correct gap.

 

ya but u can always get a torque converter upgrade and a valve body upgrade for the auto... and then auto > manual faster and easier to drive in traffic ftw!

 

Uhh, no.

 

uhh why no?

 

x2

 

x3.

 

I have to agree with CarbonXE on this. Even with those you will be lucky to be able to hold 300whp daily there are manuals putting down 500+. Manuals aren't that hard to drive in traffic unless you are really unexperienced driver or really lazy plus manual transmissions get a little higher MPG.

 

Manuals in modern cars actually get slightly LOWER MPGs. Economy is one performance measurement that the auto manages to do better than a manual. 1-2MPG is about 5-10% which is about the same % difference (lower) hp to the wheel (not a direct correlation but interesting none the less).

Scion tC auto 21/29 vs manual 20/27
Lexus IS250 auto 21/29 vs manual 18/26
Infiniti G37 auto 18/26 vs man 17/25
BMW 135 auto 18/25 vs man 17/25
Mazda RX8 auto 16/23 vs man 16/22

 

That is purely driver, I can shift at lower rpms and get great gas mileage higher than the window and have done it stock.

 

The manual gearing spins the engine faster than the auto at the same wheel output speed. A stock manual tC revs the engine 500-600rpm higher than the auto cruising at the same 70mph. The only way the manual can get better highway mileage is to drive slower unless you can find a 6th gear that drops the revs.

 

IDK i have been able to get MUCH better MPG than what the window sticker says. At one point or another, I have been able to get 35mpg highway.

I have had both an auto tC and 2 stick tCs and the stick tC is faster, gets better gas mileage, and is more fun to drive.

It is not true that most "modern" vehicles with auto transmissions get better gas mileage. Considering all things equal, the manual will always get better gas mileage - as there are less moving parts, and less power is wasted through the drivetrain. However, in the cars that you used as an example (all sports cars for the most part), the manual either has only 5 gears, and/or the gears are significant shorter.

 

Well Said!