Roman

Hmmmm I'm in two minds. My car needs 25hp more to push through the air at 200kph, which doesnt seem much. So what are we left, with, good fuel economy? Nah because the engine in the XT was rubbish. A modern engine into an XT could be interesting, but then I guess if you wanted something slow and economical, it's not like there's a shortage of other options. Then if you wanted something fast and aerodynamic, there are a lot of other options which will be more reliable. Cool gimmick factor though (the importance of this cannot be understated!) but largely pointless to own one unless you like the shape. (and fixing cars a lot) I've still super keen on a Subaru Omega/Leone coupe though, haha.

Oh yeah, good idea. I'd need to pull the dash pad back off to change any wiring though, so I think I'll be happy enough just switching the tune back and forth for now

For your claim to be true you will have found/brewed/invented a liquid with a higher energy density than petrol. This is a chart below lists energy densities of known types of fuel. Your mystery gas would need to sit somewhere much higher up the page than gasoline does but still have very similar combustion properties. (Aluminium doesnt flow through a carb and burn in a triumph engine all that well) Notice how other types of gasoline substitutes have a considerably lower energy density. Dont forget to collect your Nobel Prize on the way home today

A while back I calibrated my tacho and speedo with some custom values so they are more accurate. Lately though I've been trying to get a feel for how economically the car runs at various speeds. So I've had to to take some datalogs, and then do some maths on the logs which is time consuming and it's hard to relate back to what I was doing at the time. So I've come up with a better idea, I'm going to make it so that my tacho only activates when in 6th gear. but then the sweep of the needle will be based on a table that has Effective Injector Pulsewidth and engine RPM as the axes. The values populating the table will represent what sort of economy you're getting. So when you're driving along if the needle is showing 2k you're doing well but if it's pinned at 8k you are doing it wrong haha. When I get a new wideband and controller I'll switch to modelled fuel equation, which natively gives fuel consumption info which makes everything easier. So I could make this same thing work in all gears instead of just 6th. It would be cool if I could switch between tacho or economy gauge, either with a switch or with some logic/criteria. But I think I'm stuck with one or the other. Maybe I could permenantly repurpose the oil pressure gauge needle to fuel economy instead. And then wire in an oil pressure light, I've never liked the idea of having to look at a gauge to see low oil pressure rather than having a bright light blaring in your face to tell you there's a major problem. I've got a blue shift light mounted in top right corner of my dash cluster which works well. I've bought a second one that's red that I'm going to mount on the other side, as a general purpose "Turn this shit off somethings fucked" light that could have a few different criteria making it work. At the last superlap event, Barry manon lost a very fancy engine due to oil pressure issues. Looking back through his footage he said that his oil pressure gauge showed low oil pressure for half a lap but the oil pressure light never came on because the threshold was set too low. (something like 4psi) and no one ever looks at a gauge while you're going 10/10ths. If he had better warning it might have saved him an engine. It could be a good plan to have a warning light operated by a table maybe relating to engine rpm and oil temp, so you can run the light at say 20% below the threshold of what you'd expect oil pressure to be in every situation.

Then bought himself on aliexpress and got back here for free shipping

I'll accellerate slow-ish up to say 95-100kph Then put car in neutral and coast down to say 80-85. then accellerate again, rinse repeat. You only end up with foot on the gas for about 1/4 of the time or less because it actually takes quite a while to scrub off your speed. What I find is that I am generally travelling at the same speed as traffic around me anyway (Most of my trip to work is 80kph zone) but using 20-30% less gas.

40 litres per 100km Hahaha that is quite impressive. So from my house to Christchurch, assuming using 98 instead of Avgas would cost.... $870 each way for gas alone.

I quite enjoy the contrast between the outside of the car (swooshy lines, and quite frankly beautiful appearance) Compared to the strut towers in the engine bay (Which look like a high school metal work project) It obviously does the job etc, but just not quite what I was expecting to see!

I have been maintaing the just under/over 4l per 100km on each trip in the daily. Based on 45l tank, if I can maintain this I should be able to go 1100km before next refill. (?!) Auckland to Christchurch on a tank of gas... Which is nearly 5 weeks of driving to work and back, West Harbour to Penrose. It'll be interesting to see how the OBD2 compares to the fuel top up + check kms method though. I have started using fuelly so time will tell at next fill up... in a few weeks. It's taken hilariously long to go through just under 1/4 of a tank. On my other car, there are a few plastic underbody panels etc that have been off the car that I'm refitting to see if it helps at all. Some look to just be stone gaurds, but I think some of the other bits would contribute in a useful sort of way towards reducing drag a little.

I dont think so, if you look at F1 cars from the 60s they would have massive power V12s and skinny tiny shitty tires and were absolutely nuts to control. They all would have been way more drivable and faster with aero stuff.

Awesome! What's interesting from some things that I've been reading at the moment. Unknown to me in the 30s or whatever people had a VERY good understanding of aero stuff. (It never made sense to me that people knew how to make aircraft, but gave zero consideration to car shape) Although it still seems odd that aero downforce came into play quite late in the piece. In my mind it's always seemed that the 90s were the first sort of times that aero was considered for mass produced cars. Oh how wrong I was!

Does anyone want some free tyres? If so I'll bring them along. I've got: 4x 205/50/15 Toyo Proxes T1R. With maybe 2-4mm tread left, one has a flat spot and the other has some aggressive wear on just the outside edge, other two are pretty good. 2x 225/50/15 R888. Have had burnouts done on them so they are preeeeeettttyyyyy worn out. Good for seeing if 225 semis will fit on your car though, which is what I used them for. Still usable for a little bit longer I guess. 2x 235/50/15 R888 Same as above but a little more tread and no skids done on them. (probably still good for a trackday or two) but these are hyuuuuggggeee so not sure what they would fit.

One for Flying Brick. http://www.equipmentworld.com/dont-lower-your-tailgate-gm-details-aerodynamic-design-of-2014-silverado-and-sierra-2500-debunks-myths/

Does your carb have a return line though?

So it turns out the hilariously boxy looking Subaru XT is actually some genius aerodynamic masterpiece that spent countless hours in the wind tunnel during it's design. Clocks in with a very surprising c.d. of 0.29 Pretty impressive for something that looks like its design was based on a tupperware container https://en.wikipedia.org/wiki/Subaru_XT#Aerodynamics

+Plus a pair of widebands so we can tune it up for some epic close loop fuel economy haha. And draw some graphs of course

I thought "Hey Pete when are you getting a Ferrari" was an ongoing joke sort of like "Get a 2ZZ" Mind blown! Awesome cars man well done.

I think the benefit of the pulse and glide thing is that it lowers your average RPM to below what your final drive / gearbox / etc can actually acheive. Which you dont really get in an auto car because the revs drop when your foot is off the gas anyway. In other news. In some of the documentation for how the dual VVTI system works in the Toyotas. It adjusts the exhaust timing to allow exhaust gas back into the cylinder at cruising conditions, the reasons cited are internal EGR action but also reduced pumping losses. Would be nice to have the dual VVTI version of my engine, free 10hp and better economy. Juts a pity that most of them are completely flogged out and in need of a rebuild by now.

Ahhh nope I noobed my maths on that. Was actually just over 6. Didnt make as much difference as it does with the Echo. Yet is a lot more annoying to do haha.

In that case I think the only practical way you can measure is to fill the tank back up to the "click" at the same gas station each time.

I had a go at some "pulse and glide" in the Carina tonight. Previously just under 7l per 100km was the best economy I've managed. From tonight, 4.7l per 100km... Amazing difference! I havent managed anything anywhere near that before. That datalog though, hahaha

That's where it very much comes down to the particular engine. Probably less of an issue on modern VVTI motors buutttt The relevant term here is BSFC (Brake Specific Fuel Consumption) Basically an engine has a sweet spot where it makes the most amount of power, for the least amount of fuel used. (Based on both rpm and vacuum) So the closer you can get to your engines point of best BSFC the better. However since they generally dont give end users a BSFC map with your car your best bet is just to check with OBD2 or whatever. Looking at this example here, the best power for fuel used would be found by holding the engine at the smallest "island" Not sure what this graph is for but maybe a generator or something that's designed to just be held at max load at 1500rpm. Some car engine BSFC maps that I've seen will have the "island" at say 2/3rds throttle and 4000rpm or something like that. On a VVT engine you'll find that the lines are further apart because it holds better efficiency through more operating conditions. So 3rd or 4th gear might be in the same efficiency region.

Brake boosting and PS etc all work perfectly fine in neutral. Even if your engine is off for some reason, you would get about 3-4 full pumps on the brake before you run out of booster. It's becoming more common for cars to have electric PS as well instead of running from a belt on engine.

Depends on the car, but largely, yes that's correct. In my experience it's a fair bit of a gradient before it equals the engine braking though, I guess I was more meaning fairly gentle downhill bits.

A good example of powering through a situation where braking wouldnt work. Would be if you were in an evo rally car, and your pace notes say that someone threw their baby in a basket just behind the next crest. You have to do a sweet jump or you'll squash the baby.