Offroad-Express

hey, just bought a 1990 datsun 4x4 with a td27 in it which has had a turbo slapped on it running 7 psi and it its thirsty as. the best i have got off 60l is 430k and that is nursing it. i have done the obvious like fuel filter and air cleaner and drilled more holes in the airbox to let more air in. that helped a wee bit but not much. just wondering if anyone had any other ideas. can the fuel pump be wound down some how. it only smokes when you put your foot down and to low in the revs which is nothing out of the ordinary i wouldn't have thought.
cheers

sounds like they didn't bother fitting a boost comp to the pump. high fuel usuage is common draw back. either fit a boost comp, or a TD27T pump or wind the fuel back.
i'm not to familar with the pumps on them but if its typical VE then there usually is an adjuster at the back under a small cover. pays to get a manual/pics before playing. any mechanic should ba able to do it easy enough.

will look into it. thanks for that.

hey. just wondering wat a boost comp is and where would i get one and also is it easy to fit

boost comp = boost compensator tho it has a few other names.

basically its a diaphragm that gets inlet manifold pressure on it and it alters how much fuel the pump will inject into the motor.
it basically stops the throttle going to max fuel when there is not enough boost/air to burn that amount of fuel.

what one fits that injection pump and where to get one i do not know.

common way of doing the turbo on an atmo diesel is to use standard pump and tweak the fuel up a little or use the turbo models pump. i'm not sure if the comp off the turbo motor is a straight swap over on the atmo pump.

some aftermarket places do have comps ready to fit but are generally not cheap which is why most people simply do not bother.

tweake wrote:boost comp = boost compensator tho it has a few other names.

basically its a diaphragm that gets inlet manifold pressure on it and it alters how much fuel the pump will inject into the motor.
it basically stops the throttle going to max fuel when there is not enough boost/air to burn that amount of fuel.

what one fits that injection pump and where to get one i do not know.

common way of doing the turbo on an atmo diesel is to use standard pump and tweak the fuel up a little or use the turbo models pump. i'm not sure if the comp off the turbo motor is a straight swap over on the atmo pump.

some aftermarket places do have comps ready to fit but are generally not cheap which is why most people simply do not bother.

Lack of a boost compensator won't make you burn more fuel.
A boost compensator doesn't increase fuel when on boost, it decreases fuel when off boost. The only downside to not having one is exhaust smoke before the turbo wakes up.

Have you looked for things like mechanical drag first? Wheel bearings, tyre pressure etc.
Is the engine smoking, what colour is the smoke?
Is it harder to start than it should be?

KiwiBacon wrote:
A boost compensator doesn't increase fuel when on boost, it decreases fuel when off boost.

correct

.........The only downside to not having one is exhaust smoke before the turbo wakes up..........
.........Lack of a boost compensator won't make you burn more fuel.

not quite.
when your off boost (basically at cruise) you are able to shove more fuel in that can be burnt efficiently due to lack of air. so every time you squeeze on the throttle at low boost your shoving in more fuel than you can burn which goes straight out the exhaust. obviously not good for economy. trouble is you tend to do that a whole lot more than sitting at high boost full throttle. most people rarely use full power but that climbing up onto to boost then drop off again is done a large % of the time. so any fuel thats not been burnt efficiently starts to cost you big time.

similar to running a petrol motor rich all the time. car doesn't go much faster but by god do you suck the fuel.

you get it a lot with the common hilux 2.8 turbo conversions where they have tweaked the fuel up to much. tweak the fuel down so your not blowing clouds of smoke and you will find economy improves. down side is it limits your max power.

also don't forget 5 sec smoke means failed WOF and 10sec smoke on the road can mean your walking.

tweake wrote:not quite.
when your off boost (basically at cruise) you are able to shove more fuel in that can be burnt efficiently due to lack of air. so every time you squeeze on the throttle at low boost your shoving in more fuel than you can burn which goes straight out the exhaust. obviously not good for economy. trouble is you tend to do that a whole lot more than sitting at high boost full throttle. most people rarely use full power but that climbing up onto to boost then drop off again is done a large % of the time. so any fuel thats not been burnt efficiently starts to cost you big time.

similar to running a petrol motor rich all the time. car doesn't go much faster but by god do you suck the fuel.

you get it a lot with the common hilux 2.8 turbo conversions where they have tweaked the fuel up to much. tweak the fuel down so your not blowing clouds of smoke and you will find economy improves. down side is it limits your max power.

also don't forget 5 sec smoke means failed WOF and 10sec smoke on the road can mean your walking.

Did I mention I've spent some time experimenting with the boost compensator (aneroid) on my fuel pump.

You can't push fuel out the exhaust of a diesel without creating black smoke. On a healthy engine that'll start to smoke with an air/fuel ratio of around 20:1.
Unless you've running high boost with a serious intercooler, when moving you'll hit sensible EGT limits before you start blowing noticable black smoke.
On acceleration it's the opposite, you'll get puffs of black smoke before you hit EGT limits as the head and exhaust manifold work as a heat sink.

My boost compensator starts to work around 3psi boost and is fully open at 7psi. This on a vehicle than runs 20psi max boost and around 8-9psi at 100km/h cruise.
So at 100km/h the fuel pump is capable of delivering everything it's got. This does not result in poor fuel economy or in fuel going straight out the exhaust.

thought you might bite

your quite right. with a boost comp you won't get fuel economy which is what i said before.
its when you start pouring in maxium fuel but have minimal air is when you get poor ecomonmy. it quite obvious when folowing those vechiles by the smoke. as the vechile goes slower, rpm drops, boost drop and it starts smoking starts and gets worse untill they change down a gear or back off the throttle.

Please excuse my ignorance, but wouldn't having a boost compensator be exactly the same as having a slightly more light weight right foot?

If the only thing that controls your acceleration in a diesel is the fuel pump, (as opposed to a petrol with a throttle body controlling the airflow) then wouldn't a boost compensator be effectively letting your foot down gradually instead of flooring it while you're not on boost?

Sorry i'm fully not using the right words here and am confusing myself but all it sounds like it does is regulate the fuel flow while not boosting which is what i thought we were kinda meant to do anyway by easing your foot down and not 'flooring it' from idle coz if you do that then any diesel is gonna smoke (except this new audi a3 my mate brought round the other day mmmmm shit it could rev! whipped through the gears like a sports car!!)

please explain i'm confused;-)

ike wrote:Please excuse my ignorance, but wouldn't having a boost compensator be exactly the same as having a slightly more light weight right foot?

If the only thing that controls your acceleration in a diesel is the fuel pump, (as opposed to a petrol with a throttle body controlling the airflow) then wouldn't a boost compensator be effectively letting your foot down gradually instead of flooring it while you're not on boost?

Sorry i'm fully not using the right words here and am confusing myself but all it sounds like it does is regulate the fuel flow while not boosting which is what i thought we were kinda meant to do anyway by easing your foot down and not 'flooring it' from idle coz if you do that then any diesel is gonna smoke (except this new audi a3 my mate brought round the other day mmmmm shit it could rev! whipped through the gears like a sports car!!)

please explain i'm confused;-)

Yes that's right.
An Audi A3 diesel would make a nice shopping basket.

ike wrote:Please excuse my ignorance, but wouldn't having a boost compensator be exactly the same as having a slightly more light weight right foot?

If the only thing that controls your acceleration in a diesel is the fuel pump, (as opposed to a petrol with a throttle body controlling the airflow) then wouldn't a boost compensator be effectively letting your foot down gradually instead of flooring it while you're not on boost?

Sorry i'm fully not using the right words here and am confusing myself but all it sounds like it does is regulate the fuel flow while not boosting which is what i thought we were kinda meant to do anyway by easing your foot down and not 'flooring it' from idle coz if you do that then any diesel is gonna smoke (except this new audi a3 my mate brought round the other day mmmmm shit it could rev! whipped through the gears like a sports car!!)

please explain i'm confused;-)

thats about it. basicly going easy on the throttle till you have enough boost, more importantly is to take foot off the gas when boost drops off. trouble is most people can't do that and even the experenced have trouble doing it especially if your limited to 1/4 throttle while off boost. most peole cannot tell the differece in feal from 25% throttle and 40% throttle.
boost comp just makes it so much easier.

Fogg some lpg into it that will burn all the diesel and give you up to 50%more power

long wrote:Fogg some lpg into it that will burn all the diesel and give you up to 50%more power

While putting your EGT's through the roof and overstressing the block through pre-ignition.
Not a good plan.

its dosnt preignite the amount u use is so small a 9kg bottle lasts for 5 tank fulls of lpg

long wrote:its dosnt preignite the amount u use is so small a 9kg bottle lasts for 5 tank fulls of lpg

It does preignite (despite the BS marketing claims to the contrary), the auto-ignition temps of LPG are far lower than your diesel cylinders reach before the fuel is ignited.

Simply running lpg into the intake of an idling diesel gives you audible detonation.

Comparison of Auto Ignition Temperature

The auto ignition temperature is the temperature at which a fuel will ignite without the need for a spark or flame. In respect to auto ignition temperature LPG, CNG, and LNG are much safer than gasoline or diesel because the auto ignition temperature is much higher. The following chart compares the auto ignition temperature of various fuels.

http://www.propanecarbs.com/propane.html

however one thing you need to watch.... oil getting into the motor via breather or leaky turbo can preignite and increase the in cylinder air temp which can cause the lpg to preignite.

it all depends on how hot the air gets under compession and especially so if you have the boost wound up.

tweake wrote:Comparison of Auto Ignition Temperature

The auto ignition temperature is the temperature at which a fuel will ignite without the need for a spark or flame. In respect to auto ignition temperature LPG, CNG, and LNG are much safer than gasoline or diesel because the auto ignition temperature is much higher. The following chart compares the auto ignition temperature of various fuels.

http://www.propanecarbs.com/propane.html

however one thing you need to watch.... oil getting into the motor via breather or leaky turbo can preignite and increase the in cylinder air temp which can cause the lpg to preignite.

it all depends on how hot the air gets under compession and especially so if you have the boost wound up.

My engine (17:1 compression) suffers preignition when drawing in lpg at idle when cold. It only gets worse when you're warm and running under boost.

The diesel auto-ignition temp is much lower, but it can't pre-ignite because it's not there until it's wanted.

ive had no probs with running LPG in my diesels ive been running it in the last 3 4x4s ive owned with no failures to date

long wrote:ive had no probs with running LPG in my diesels ive been running it in the last 3 4x4s ive owned with no failures to date

So given you installed it in 3 4wds, I'm guessing you didn't own them for long? Did you tell your insurance company and what did the say?

Hi guys. Hope this isn't to late to get into this discussion, but I too have a very thirsty TD27. Trying to locate some shop service manuals here in Canada is tough though. Couldn't advanced timing or bad injectors cause this to happen? I'm new to the diesel scene, but this is what I've been told.

myronn wrote:Hi guys. Hope this isn't to late to get into this discussion, but I too have a very thirsty TD27. Trying to locate some shop service manuals here in Canada is tough though. Couldn't advanced timing or bad injectors cause this to happen? I'm new to the diesel scene, but this is what I've been told.

Overly advanced timing will show as black smoke under hard acceleration and a relunctance of the turbo to build boost.
Worn or coked up injectors can show a range of symptoms ranging from smoke to noise. I recently had my injectors done ($700 thank you), the shop that replaced them said 3 were completely shot. My fuel economy hasn't changed but it does run cleaner at idle when cold.

timing generally doesn't change especially with timing chains. heard of some with stuffed pumps but they where blowing white smoke. whats common with toyotas is retarded timing, use lots of fuel, has lots of boost but no power. i would have thought if timing was too advanced you would hear it knocking badly ??

if it runs cleaner at idle it sounds like blocked up airfilter (new filter do not clean the old one), faulty egr (disable it), or low compression. the other possibility is worn valve train. i think its that model thats prone to wear in the valve train which means valves don't open enough and you don't get enough air into the motor.