Speed Density Thermostat Selection?
Thread Starter
Le Mans Master
Joined: Aug 2000
Posts: 6,273
Likes: 14
From: Austin TX
Speed Density Thermostat Selection?
My 71 has a speed density from a 90. My local speed shop mechanic says I should use a 160 thermostat (which I have installed). Mark Campbell of Street and Performance says I should use a 180 or 190 since a 160 will always tell the ECU that the engine is cold and will richen the mix.
I seen to be getting poor gas mileage although performance is good.
Any recommendations?
I seen to be getting poor gas mileage although performance is good.
Any recommendations?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Speed Density Thermostat Selection? (flynhi)
With all the electronics from a '90 Vette you should have no problem running a 160 deg stat & fan switch. The ECM can go closed loop well before the theremostat opens.
If mileage has fallen off, use the test on my site (link in sig. below) to see if the ECM is going into/staying in closed loop mode. If not check your O2 sensor and the coolant temp sensor as problems with either will prevent closed loop.
In closed loop the ECM will use the O2 sensor data to maintain the stock A/F ratio. Be aware that a leak in the exhaust system ahead of the O2 sensor could also throw off the ECM readings and cause a rich condition.
If mileage has fallen off, use the test on my site (link in sig. below) to see if the ECM is going into/staying in closed loop mode. If not check your O2 sensor and the coolant temp sensor as problems with either will prevent closed loop.
In closed loop the ECM will use the O2 sensor data to maintain the stock A/F ratio. Be aware that a leak in the exhaust system ahead of the O2 sensor could also throw off the ECM readings and cause a rich condition.
Safety Car
Joined: Feb 2001
Posts: 4,397
Likes: 0
From: Looks like I picked the wrong week to stop sniffin glue Orlando
Re: Speed Density Thermostat Selection? (flynhi)
Iv got a 90 with the speed density, and a 160 stat. Works fine, iv never had a problem.
I also have the Craig Moats software for monitoring the ECM, and you can watch it go into closed loop.
:chevy
I also have the Craig Moats software for monitoring the ECM, and you can watch it go into closed loop.
:chevy
Burning Brakes
Joined: Jun 2003
Posts: 949
Likes: 0
From: smithtown ny
Re: Speed Density Thermostat Selection? (flynhi)
i have a91 vette with a 160 stat i have no problems but i also use a 3 wire heated oxygen sensor i do have headers but it will still keep the car from going in and out of closed loop.
