BritishV8 Forum

22 lbs

Seriously? Very good.

Shouldn't be too hard to take a couple more pounds out of it too.

I've improved my tune quite a bit since August, so I thought I'd upload the updated tune file.

This one is much more fuel efficient: My-Buick-Rover-V8-MS3-EFI-Tune.msq









Comments welcome.

Curtis, Looks good. I have heard that 12.5 AF for full throttle,13.5 for acceleration and around 14 at idle, but what are you gaining by going over 15 at cruise RPM?

Any one know if a Rover pressure plate will work with a Mustang disk? I am using a T5 with a 10 spline input shaft. If I have to will drill new mounting holes to mount a Mustang plate, but would love to know if I can get away with not.  

Curtis, nice looking msq.

Should work fine, most clutch discs are about the same thickness.

Jim

Quotewhat are you gaining by going over 15 at cruise RPM?

Fuel economy to/in/from "The Blacklands" averaged ~2.1mpg better than my cross-country trip on the old tune.

I'd hoped for more improvement! I averaged 24.1mpg, running E10 the whole time and mostly driving "normally" rather than trying to get good mileage.  All sorts of roads and speed limits, including 35mph park roads and 80mph highways. Some rushing to get to Moss Motoring Challenge destinations before sunsets. So maybe 24 isn't "bad", but I believe I should be averaging 28 or 30mpg (U.S.) overall on road trips.

As I read up on the subject, it seems I've been overly cautious. Apparently, "cruise" AFRs in the 16-17 to 1 range are common. Even the most conservative articles I've found suggest a target around 15.7:1. But I'm not sure exactly how they define cruise.  

A few words about the maps above:  The y-axis correlates almost directly with MAP sensor measurements (of manifold vacuum). I only get into the bottom "25% load" row when completely off the throttle and decelerating hard (i.e. engine braking). Touching the throttle or clutch pedals will immediately lift me out of that row. Typically, if I'm in the 30 or 35% rows, it's because I'm feathering the throttle pedal to slow my rate of deceleration. I can generally maintain speed on flat ground in the 40, 45, or 50% rows (depending on speed, gear, wind, etc.)  When my engine is warm, it idles at 40% load and ~870rpm. If it's cold, higher. Acceleration at wide open throttle will put me into the 85% row. I wonder if a better flowing exhaust system might help me get into the 90% row. (Boost from a supercharger or turbo lets some people go way beyond 100%.)  

So, to my way of thinking, cruise means 40-50% load at 1700+ rpm.

One reason I've been cautious about going leaner is higher temperatures. I don't have a way to measure combustion or cylinder head or even oil temperature. Just based on coolant temperature, it seems I have a long way to go. On both trips (and in fact ever since I installed EFI)  my coolant temperatures tend to run in the low to mid 160s while I'm driving. I should replace my 160 degree coolant thermostat with a 180 degree thermostat.

I logged data on three different stretches... 25-35mph on a twisty road, 55mph on the main Black Hills park road, and 75mph on an Eastern Wyoming byway. If anyone is interested, I could extract a few screen shots from MegaLog Viewer.

Thanks, Curtis!  I had no idea you could run that lean. There might be a gauge diesel truckers use to monitor exhaust temps when they upgrade their Turbo's. I would look at my spark plug insulators(bright white instead of tan) and exhaust pipe tips (frosty white)as too lean indicators. Speaking of spark plugs a lot of guys are switching from AC to NGK projected nose for wide heat range. I think they are gapped at .040.

I use an EGT gage plugged into one of the headers where the O2 wideband sensor is on the other side, in the collector. I Shoot for temps approaching 1500* that far from the ports. I think you can go to about 1800 at the ports. On a long upgrade you can watch EGT and water temp to dial in the timing advance. You want to keep the heat in the engine instead of the pipes but not make the coolant start creeping up on you as you go up the hill. Once that's sorted it's easier to lean the mixture. That will usually show up as elevated EGT readings without much effect on the coolant to the best of my recollection.

Jim

Just for the record, my Innovate wide band tailpipe sniffer with 17" extension says I am at 15.6-15.8 at cruise. At cruise to me means 2600-2900rpm (75-80mph) on level Interstate on cruise control. Changes about a point either way if going up or down hill. This yields 25-26mpg on E10 with a carburetor.  I can live with that.

4.0 Block ready to assemble

re: "4.0 Block ready to assemble"

I'm envious! Surprised to see the black finish though.


re: "...my Innovate wide band tailpipe sniffer with 17" extension says I am at 15.6-15.8 at cruise...."

I may get there or beyond yet. For the time being, I've installed a warmer thermostat and adjusted my AFR table 2 baby steps leaner. I'll be curious to see if fuel economy changes noticeably. Just one more roadtrip planned this year...

(I adjusted the VE table too, using VE Analyzer.)

Here is the next step, The flywheel with 10" Mustang clutch plate mounted and balanced will be back from shop Fri. Should have motor/trans mounted in car by end of weekend.  The plenum Bottom plate is being cut down and we will be test fitting to see if we can clear the hood.

Side view

Then the fun begins wiring up the Megasquirt V3.

What pilot bushing should I use to match the T5 and rover crank?

10 inch Mustang pressure plate mounted on Rover flywheel. nice fit.

Rover Meet T5.  Soon to be installed

McLeod Racing throw out bearing/slave

passenger side header pass throw hole

Drivers side header pass threw hold

Need some info, I have seen in Jim Stuart's photo's and write up that he is using a serpentine belt. the question is how much of a difference is there between the 3.9 and 4.0 front cover. my front pulley is 5 in from block to outside edge.  that doesn't appear to be enough room to mount an alternator.   So any one got a good photo of a set up or know what will work?

Late 3.9 front covers are identical to the 4.0 in Discoveries.

'94/'95 Discos and '95 RRCs with 3.9s and 4.2s used the same front cover. The dimensions are identical to those used in Discos through 99-1/2 (GEMS EMS).

The earlier engines with the distributor driven oil pumps had shorter crankshafts than those with the crank-driven oil pumps.

All of the Rover V8s had the alternators mounted up high

Very interested in this thread since it's the same kind of build I'm doing. 4.6L GEMS, GM T5 and converting to megasquirt 3.

Keep us updated!