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Originally Posted by diabolical1
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Originally Posted by NoDOHC
... but the 4-port stomps the 6-port above 1800 rpm. Meaning that you get better grunt, even on the interstate in high gear. Idle is good and mileage doesn't suffer much (35mpg 6-port -> 30 mpg 4-port with NA 5-speed, 25 mpg 4-port with turbo 5-speed).
The 4-port is easy to work on (all kinds of space where the turbo is supposed to go), runs cooler (could be from the lower compression ratio) and is much simpler to tune.
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this is going to sound way more confrontational than i mean it to be, but where are you getting this from? i'm MOSTLY interested in the parts i bolded, but i'd like to know for the sake of curiosity and/or possible learning, about everything you mentioned. |
You will certainly have to sound a lot more confrontational that that before I will interpret it as anything other than seeking clarification.
The numbers for the torque curves are slightly skewed, as I compared a mildly ported 4-port with a heavily modified intake setup to a stock 6-port with 195,000 miles on it. The 6-port did have a higher compression ratio (9.4:1 vs. 8.2:1 - in defense of the fairness of the comparison).
Preliminary data (halted by an inopportune failure) would indicate that the 4-port makes more torque than the 6-port at 1,000 RPM if they have the same compression ratio.
I compared the torque curves from dyno runs of the two engines and computed the VE curves from known injection durations from the datalog taken during each dyno run and the AFR which was logged during the dyno run. Same dyno, same AFR gauge, same ECU (the numbers may be wrong, but they are consistant for comparison).
The following torque chart is made in Excel, but the numbers came from two dyno charts (in this case they were both from the G-Tech on the same stretch of road).
The mpg data is taken by me as I fill up a tank of fuel. I keep a running average (with outliers discarded) for each car, so I was able to simply extract the data from the chart and present it above. Actual data (with more miles on the 4-port) is: 6-port = 32 mpg city, 38 mpg highway, 4-port = 22 mpg city, 29 mpg highway (numbers above were early in the 4-port engine's life and I was babying it at the time).
EDIT: Actually, I forgot that early in the 4-port's life I was using NA drivetrain, which gave a 0.69 Overdrive. I am not sure if I was babying it or if the NA drivetrain was that much better for mileage.
Higher compression rotors help the 4-port, but I don't have enough data to express exactly how much.
My first seven tanks on the new build:
18mpg (mixed driving/idling/tuning)
24mpg (3/4 mixed driving 1/4 highway, low-speed VE improved significantly towards the end of the tank)
27mpg (1/2 highway, 1/4 mixed, 1/4 city)
28.5mpg (3/4 highway, 1/4 city)
31mpg (All highway)
31.2mpg (3/4 highway 1/4 mixed)
30.8mpg (1/2 highway, 1/2 mixed)
For running temperature, I am only looking at the ECU data logs and observing that the 4-port ran about 4 degrees C cooler on average than the 6-port. The two engines used the same water pump and thermostat, as I had already tapped it for the Haltech sensors, so this to me was a marked change.
For ease of tuning, you didn't have to worry about where the ports open at various throttles (which makes a difference when you are tuning with speed/density).
I hope this helped you some.