Diamond Larry’s 1999 Saturn SL2

[diamondlarry]

My Ride.

Larry Towbridge - CleanMPG.com - Dec. 28, 2006.

My car is a 1999 Saturn SL2 5-speed. It has a 1.9L DOHC 4-cyl. Hence the name, DOHCtor Green MPG . I purchased the car for $2800 from Saturn of Paramus in NJ. I have been averaging 50.7 MPG since I started driving it in September. The best tank I've had was 55.4 when I drove to Tom's house and back for the MHG meet in Oak Creek. I make extensive use of P&G since I have wired up an injector kill switch. My tires are pumped to 60 psi. The cylinder head has been modified by Mike Hollar of Power Haus. It had .050" milled off along with other mods to the combustion chambers and intake ports that promote more efficient combustion. The cam gears have been off-set to allow for an improvement to the cam timing. A side benefit to these mods is that power has been increased by approximately 30%. Thanks to much advice from Wayne, I have been able to keep myself from using that extra power... most of the time

[antrey]

Looks like you'll hit elite hypermiler status within the next couple of tanks.
Congratulations! What tires are you currently running? 60psi seems a bit high.

[diamondlarry]

I'm running Goodyear Assurance Comfortread's. They are 185/65-15's. The max sidewall pressure is 44 psi. I have run at this pressure for several thousand miles and have seen no adverse treadware. I have had them as high as 70 for a short time. I want to point out that tire pressures are definitely something that is a matter of personal prefference.

[antrey]

I've slowly inched the pressure up on my tires, giving me the chance to get used to the increased noise and vibration.
The full wheel covers I installed seem to have reduced some noise but it's just a subjective sense. I started at stock
32psi went up to 40psi then 46psi and finally at the 50psi I'm running now. I saw a definite increase in mileage at each
pressure and feel its well worth the increased noise. As positives, steering response and feel is much improved and
there is no longer any sidewall scuffing during spirited cornering. When I get around to purchasing my Scan Gage II
I'll run a more definite study to plot pressure Vs FE at various speeds and maybe perform a noise study as well.

[antrey]

When did you perform the engine modifications?

[diamondlarry]

Originally Posted by antrey

When did you perform the engine modifications?

Unfortunately for baseline purposes, the mods were done before I ever picked up the car. I bought the car from from the NJ dealer and I wasn't able to get enough time off to go get it.(12+ hours one way). My friend that lives in central PA went to the dealer and picked it up. He did the head-work while I was waiting to get the time to come out and get it. I picked it up in late September. He has driven numerous turbo Dodge cars that were rated at ~150 hp and he thinks that my car drives like it is stronger than that. The head milling brought the compression ratio up to around 10.5:1 and I get no detonation on 87 octane even when doing a full-throttle acceleration in 5th at 20 mph with 4 people in the car. I'll dig around my computer and see if I can find some pics of the headwork.

I'm pretty sure you'll find that there is a psi point where FE gains level off. I have also noticed better handling at the higher pressures. The only negative is when there is loose dirt/water/snow on the road.