Extra gauges for a turbodiesel
 

Hello all,

I'm planning to install cruise control and a MPGuino on my car and as those two requires a lot of work behind the dash, I've decided to think of other things I can do at the same time, to save time, and someone suggested getting some gauges.

My 1.7 turbodiesel already has tacho, speedo, fuel and water temp (only shows temp between 70 - 110 deg C though) gauges and that's it.

What other information would be useful to help me improve my FE? A boost gauge? I.e., the lower boost, the better? Would that work on a diesel? Any others? Am I correct in thinking a vacuum gauge is useless on a diesel considering diesels don't create vacuums?

A voltmeter and an oil pressure gauge would be nice but those won't contribte towards hypermiling.

My car doesn't have an OBD-II port so can't use gauges that needs the OBD-II port.

Thanks for your time in advance!

Measuring volts may be useful if you plan on installing an off switch for the alternator. Measuring amps would be better: it tells you how much electrical load is on alternator, and so on the engine.

Maybe so, but I wouldn't want to send my entire electrical system through the ammeter which would need hefty cables to and from the battery?

Would an air/fuel ratio work on a diesel and would it be useful at all?

I would think that the Air fuel ratio might come in handy, though I have never seen one for a diesel, I am sure that they sell them.
In a diesel I think the ratio of air to fuel is 100:1, whereas in a gasoline (petrol) engine it's 14.7:1. So any changes that are made to your engine will have to make major swings to get rich or lean in comparison.
As far as the Turbo is concerned, you want to have quite a bit of boost, so don't turn it down. If anything, turn it up. I am not sure what pressure diesel runs most efficiently, but the higher the compression ratio, the higher the efficiency. check what others are running and tune your engine accordingly.
"Diesel engine

In an auto-ignition diesel engine, (no electrical sparking plug--the hot air of compression lights the injected fuel) the CR will customarily exceed 14:1. Ratios over 22:1 are common. The appropriate compression ratio depends on the design of the cylinder head. The figure is usually between 14:1 and 16:1 for direct injection engines and between 18:1 and 20:1 for indirect injection engines."
Check out this Wikipedia article for more info, hope I helped.

I see what you mean, but reading the Haynes manual for my car (found here) and when explaining how the fuel injection system work, one section says:

"A turbocharger is fitted to increase engine efficiency by raising the pressure in the inlet manifold above atmospheric pressure. Instead of the air simply being sucked into the cylinders, it is forced in. Additional fuel is supplied by the injection pump in proportion to the increased air intake".

Note "Additional fuel". That's not quite what we want? BTW the Haynes manual mentions the compression ratio for this engine is 18.4:1 even though it is direct injection.

Thanks for your help, much appreciated!

It's very difficult to get an air/fuel ratio gauge for a diesel, so I'm leaving that out.

So it boils down to 4 gauges:

Turbo boost
Exhaust gas temperature
Voltmeter
Oil Pressure

I can only have 3 gauges. Keep in mind that the EGT gauge is very expensive, and I'm worried about the sensor breaking off and messing up the turbo.

Which gauge should I drop?

If it is possible to get a mpguino derivative working reasonably well on your vehicle (I don't know anything about astras, or a lot of other vehicles for that matter) that would be your %99 return.

EGT (exhaust gas temp) gauge will tell you the most about your motor. When Exhaust temps are high, it is usually because you have inefficient burn and some of the fuel is finishing combustion after the power stroke.

If you plan to tune the motor, one of the first 'tricks' is to turn the fuel up or down (up=more power, down=more economy... to a point!). If you do that, you'll need an EGT and pyrometer (the pyrometer is what reads the temp, the gauge displays the results, EGT is what is being read).

If you are really worried about the turbo being damaged by the pyro, then install it after the turbo. It won't be as accurate, and will certainly read much lower than before turbo, but it will still give you an idea as to the relative changes in fuel load.

It will also allow you to fiddle with your boost settings, which can yield a big increase in power or economy. Basically: as your motor gets more load, boost should go up to a given point. I don't know your motor so I won't suggest maximum boost settings as too much boost will pooch the motor for sure. For a large 6cyl Toyota diesel (4.2liter) "normal" boost is up to about 13psi. Some folks run 16 w/o issue. For a large cummins motor, I've heard of people running into the 30's without issue.

As boost goes up, EGT's are likely to spike (compressing air heats it). You want boost, you don't want high exhaust temps as you can easily reach temperatures in which you start to run the risk of damaging internal parts.

Short answer: I'd add EGT and Boost to any diesel. Period. Beyond that.... Oil pressure doesn't tell you much besides "time to rebuild". Several gauge companies make combined gauges for stuff that doesn't need high resolution- like oil px or voltmeter.

Should I get EGT and boost even though I'm not looking to tune the engine or fiddle with the boost settings?

Can I use a petrol turbo boost gauge and ignore the vacuum scale, or do I have to get a specific diesel boost gauge which I've not found any so far?

I would like a split oil pressure/voltmeter gauge but again, I've not found that sort of thing anywhere apart from an incredibly expensive digital gauge which I'm not going to get.

boost is boost- gas/diesel doesn't matter

EGT and boost are such useful information, that I would get them regardless of your plans to fiddle with the motor settings. But the EGT gauge is expensive and may not be as important to you.

Look on autometer.com or egauges.com for combination gauges. I have no affiliation, but have been pleased with their information in the past.

Been watching this. Most EGT's uses a stainless sheathed Thermocouple. There is virtually no likelyhood that the sensor will break. At the temperatures that would damage it, your engine is already toast. No Worries. I've run them in extremely high performance applications with no failures.

As far as running at low boost, this is something you will want to talk to your auto tech about. We don't have engines like your particular one over here in the states, so I haven't seen how your induction system works. I understand that it uses an EGR system to rebreath exhaust gasses to increase efficiencies. This only occurs at cruise speeds. The addition of inerts from the exhaust stream reduces the amount of fresh air and fuel required. It also reduces CHT's (Cylinder Head Temperatures.)

Most diesels only control fuel to the intake system. There are no throttle plates controlling air intake. (In most cases.)
By running forced induction, the apparent displacement of the engine is increased. This increases power, or in our case, allows us to operate more efficiently doing work.
Your waste gate is used to increase low speed engine performance. A non-waste gated turbo only produces boost when high loads are present above a specific engine operating range. They are necessarily sized so that they don't over-spin. As you increase load, your waste gate bypasses to maintain a maximum boost value. Basically it just dumps excess air charge.
At low RPM load, the trim and turbo sizing is setup to provide more available charge to accelerate the mass of your car. Work.
The boost will build as the engine speeds up, to either a pre-programmed maximum, or a mechanically imposed limit. I expect your engine has a computer controlling that maximum boost.

Be careful with modifications to the fuel system. Too much fuel to the system based on the amount of air being taken in can drive EGT's too high. Your pistons will start melting if it gets too hot in there. I don't know how your head and exhaust system are set up. Some engines use aluminum heads with steel or alloy liners in the exhaust ports to keep the ports from flowing. Those sleeves deteriorate over time in high temperatures.
Messing with the fuel injection requires keeping close track of temperatures. Without an EGT, playing with the injector pump delivery can result in catastrophic engine failure. Your engine may already track EGT with it's computer. I just don't know.
Simply arbitrarily reducing the boost limit will result in excess fuel in the available air charge at high throttle settings, and your EGT's can go too high. Fuel delivery must be reduced to match the available boost. Excess air doesn't hurt you. It's too much fuel that will do that trick, as a previous post explained.

Based on all that, just use driving technique to improve things. You have a tremendously efficient engine. Keep it in great shape, and drive with care. It will deliver exceptional economy. I wouldn't mess with it myself, and I've worked on a lot of OTR and Commercial Diesels. There's just too much going on there. Consult your mechanic about reducing the fuel delivery or better yet, just keep a light foot. :thumbup:

CJ

Wow awesome post! I've learnt a lot - thanks! I'm not looking to touch the engine really, I'm happy with it. I'm just wondering whether an EGT gauge is worth it if I'm not touching the engine. sandcruiser seems to think so. I might not get it as it's quite involved to get the exhaust manifold off as the turbo and the manifold has to come off together, and the gauge costs a fair bit. I can do it, but I don't think it's worth the Effort.

Thanks again for your post!

Absolutely! Get both the EGT and Boost gauge.

Happy Motoring!

CJ

if you aren't going to adjust any settings at all on the motor, the EGT gauge would really only serve to tell you if something is very wrong, and might not be worthwhile.

The only other advantage to the knowing your EGTs is knowing how long to idle down after driving to give your turbo a chance to cool. If you push the motor hard, then shut it right off, you can get coking of oil on the turbo bearings- which will shorten the life of the turbo. Knowing the EGTs will let you shut down the instant it cools to a reasonable level. "Reasonable" is open to some debate- I figure anything below 400*F is fine. Some folks insist that 200 or 300 is the magic number. Idling to cool the turbo wastes fuel, but extends the life of your turbo, your head, the valves, and even the motor oil. A faulty turbo will waste far more fuel than the amount your motor consumes at idle for 30 seconds every now and then.

A boost gauge should be cheap(ish) and will give you an idea as to how hard the motor is working... ie: how much load it is experiencing. With practice, knowing the boost level should help you gain mileage, I think.

I like gauges, so I find it easy to justify installing as many as I can. But if you aren't likely to make changes in the fuel delivery system, EGTs aren't the most pressing thing to monitor.

I would think that it would be fairly easy to just create an oil pump run-on circuit with a timer for such an issue. If your oil pump is electric, or can be converted to electric, you could just make a system that let the oil circulate in the sump, through the turbo, and not even be idling. That would prevent coking and cost no fuel, best of both worlds. It would run off battery power after you shut down the engine. Just throwing ideas out there, I know some of them might not be cost effective.

EDIT: I just Googled this and came up with a website that does this specifically. They use this application for race engines to prevent coking. The Prices aren't that bad in my opinion, though it might cost about $300 or so for a setup that fits you. Check it out: RBRacing

interesting link
I've found that idling for as little as 30 seconds usually gets me down to reasonable temps.
I'd guess that $300 of fuel is an awful lot of 30 second idle shutdowns

and...
it isn't just oil that's involved here. Running the motor allows the head itself to get cooled, and the exhaust manifold.

To some extent I suspect that you've got to balance out the fuel wastage with the the long-term engine care.

Not as many as you would think, however I am talking about the saved time, as well as the saved fuel. If you add up all the 30-90 second wait periods you would have to endure over the course of owning the car, hours of time would be spent waiting. One has to calculate worth per hour.

Unless you're running this car on the track, engine temps are not going to get that high to cause the head or manifold to warp, if they do then there are more serious problems than the turbo coking up.
Besides, through thermal convection, there still still be some flow preventing hot spots. If you're worried about the cooling of the other engine components that much, just get an inline pump that turns on when the turbo timer kicks on. Then you have the best of all worlds, no fuel spent idling, turbo cools off for no coking, and the engine has coolant circulating to prevent heat damage. :thumbup:

Funny:

your points seem valid. I still have a hard time believing that it won't cause damage if I arrive at home with 600 or 700 degree EGTs, and just shut down.

But I can't pinpoint what the damage would be.

Thanks for your input!

Few things to keep in mind.
1) Get a Boost gauge; not a boost + vac gauge (diesels don't typically have Vac.
2) EGT is nice Have one on my Gasoline car; need one on my Diesel.
3) Coolest Turbo Diesel Gauges McNallyelectronics.com : Home (Expensive though)
4) MPGino is super cool and *should* be able to be adapted fairly easily.

* I feel all this electric pump, or turbo timers are all a little over the top just to avoid 10 seconds of waiting to turn off the engine for me, considering the age of the car.

* Not going to get an EGT gauge. It is nice and might be useful, but I can't justify the $80 minimum cost. I've decided on a boost, oil pressure and voltmeter gauges.

* Dremd - I can't find a boost only gauge *anywhere*, and I'm sure if I do find one, it'd be quite expensive. I don't mind having to live with the vac part that will be unused.

Thanks to everyone for all your help, much appreciated!

I read on the Peugeot forum that the turbine in a turbodiesel has some kind of boost sensor (this was a thread about someone's turbo malfunctioning). Can the data from this sensor be utilized, or is it some low level, ECU-only stuff?

Yes, I just spotted that in my Haynes manual this morning. However, I don't know whether I can tap directly into the sensor or it is using a specific method of communicating the data to the ECU. Not sure how I would be able to find this out.

That's actually the set my tdi came with. If you keep your eyes peeled you may find a used egt gauge . . .

Amazon.com: VDO 150052 Boost Gauge: Automotive $27
Is the one on my car;

The cheapest I can find that gauge in the UK is $85 and Amazon.com refuses to send it to the UK for some strange reason.

I was just coming to the same conclusion myself.
PM sent.

Cheap EGT stuff
 

I was looking at this a while back...

Aircraft stuff looks like it might work... ConAir Sports Ltd

Not bought one myself though (yet).

Thanks!

Already got one thanks to dremd - was mighty kind of him to send it to me. Unfortunately not installed it yet! Hopefully next week as I got a week off work.

Hi,

Just a thought have you considered a TUnit or something similar ? - I think they match an eco4 engine (CR Diesel ?).

They are normally associated with more power but at "min" setting they may give you an economy edge. You may also find a higher power setting results in more economy with different driving techniques especially in the UK with our absence of long, straight highways.

Do you mean this? I've already considered it, £450 seems like an awful lot for possible fuel savings that isn't possible to calculate until it's installed, also my car's 8 years old with 85,000 miles on the clock, I don't think I'll make the money back in fuel savings.

BTW my engine doesn't have common rail injection - just the bog standard direct injection. Opel/Vauxhall didn't use common rail injection on their diesels until 2004, well after everyone else have changed over. However, there is a tunit available for my car anyway.

I'm just being curious but why did you copy my post from a few months back...?

Cool, there are so many DI, CR and so on variations of GM Diesel. I used to have an Astra with the Isuzu engine and before that a Nova TD.

Good luck, I shall follow progress. :thumbup:

Yeah, my engine was made by Isuzu as well. They seem to be well regarded as opposed to Vauxhall/Opel's own diesel engines.

you can find a boost gauge in a junk yard for a few quit. if not pull an MPG
gauge out of benz and reorient (clock it differently) it will do pressure as well as vaccum. great quality gauges.

also might i suggest an AIT gauge. interesting to see economy changes with warm and cool intake temps.

i had an isuzu once an 86 imark/kadet with NA 1.8 IDI - good engine!

Already brought a boost gauge months ago. Need to get around to fitting it tho. Sigh.

Don't most modern cars have an external temperature display nowadays anyway? Maybe not as accurate as an AIT gauge but wouldn't be very much different. Even my cheap bottom-of-the-range 8 year old Astra has one and it doesn't even have ABS. But on the other hand, all post 1996 cars in the USA can use a scangauge which will display the AIT anyway? Unfortunately my car doesn't have an OBD-II port so I can't use one :-( I've now got 4 gauges to fit and nowhere to fit 2 of them! :-) Would prefer a EGT gauge over an AIT one anyway.

So far in my experience there's not a lot of variation in relation to temperature for my engine. If you look at my fuel log you'll see the consumption have stayed fairly static despite a temperature range between -1 to 15 deg C since August. In fact the best tank was recorded on the hottest day of the year! This despite ppl telling me diesels get better MPG when its cold. Ah well.

who told you that? that is an extremely subjective statement.

You're not doing too bad as you are, I'm struggling to get an average of 60 MPG Imp on mine. Temp seems to make no difference either, I theorised that the air going through the turbo etc. would sort of smooth out any cold / warm extremes.

*Holds hands up* I'm only telling you what most people have told me. Read this page - this is where people told me diesels get better MPG when having colder air intake.

Actually, I'm fairly disappointed with my MPG figures! But I know I won't get significant increases without big spending or big modifications.

Anyway, what about the air flowing through the intercooler? Wouldn't different air temps cool the air differently?

Yeah, my thought was though that without them then the turbo would basically warm air to the same degree - turbo temp being controlled elsewhere. A debate has been had in VRS circles about whether the PD160 intake from the equivalent SEAT helps power by allowing air to be cooller when it goes in, but my thought is that it makes little / no difference.

I would be interested in your techniques though. I did a tank at 60 or less and only got an additional 5 or so MPG over my normal leaden foot.

I don't really use any specific techniques - my commute to work is pretty much flat so I just set the cruise control at 60mph and aim the car where the road goes. The motorway on my commute is mostly 2 lanes which is annoying, makes it hard to overtake lorries (which trundle on at 54mph) without someone driving up my tailgate. There are billions of lorries on the M18/M62 for understandable reasons!

In cities, I try to brake as little as possible, and learn all the signal timings - it has gotten to the stage where at 4am, I drive at 10mph for a mile at a specific section of my commute, while someone else is booting it at 40mph, and when we both arrive at the final set of traffic lights, I've timed it so as soon as it turns green, I shoot past him and drive up the dual carriageway at the speed limit, then wonder how much fuel he has wasted driving at 40mph between traffic lights. It's a lot harder when the roads are not empty like 4am, so I just try to drive as smoothly as possible without pissing off too many people and minimise use of the brakes.

I use DFCO to slow myself down when driving downhill and in a speed limit zone, and coasting when going into a lower speed limit zone, and if not enough distance to coast, I use DFCO.

I try to park facing out - as my engine takes literally 15 minutes to reach its operating temperature of 87 deg C (really must check that thermostat).

It's hard to get good MPG out of my car when doing city driving as the environmental mods done by Vauxhall doesn't work at speeds under 40 MPH, and my car's very heavy. My Astra LS ECO4 gets the exact same urban MPG as a standard Astra LS

Interesting. I'm still experimenting with some techniques. Its fun but my overall results are still disappointing so far.