Thread: turbo fitted and running

Originally Posted by lambrover

so has anyone changed there pump timing?

I think my pump was played with prier to me owning it and adding a turbo the lock wire had been cut.
When I took the car for its first run with the turbo I left the fuel alone I was only getting 6 to 7 psi very late so I couldn't leave it like that so wound it up some, but some of you guys have wound the pump up heaps, most of you have intercoolers as well don't you, that is probably the biggest differance.

Stock, the full load and max speed screws have tamper proof shrouds.

If the pump goes to a diesel shop, they use wire and a lead seal on the screws to stop tampering.

Your turbo has a wastegate (some/most stock 4BD1T are free float), so you have both the wastegate, and the full load screws to adjust for boost pressure.

You have only mentioned adjusting the full load screw! Have you checked what pressure your wastegate is opening at?

Intercoolers don't help that much at low boost pressure.

Once you are over about 12 psi you may start to notice a difference if an intercooler is fitted. Some here are running much higher boost without an intercooler.

I am not saying they are not useful/helpful, just that you shouldn't think they will make a big difference at those levels of boost pressure. However if you run high fuel and boost pressure settings, a good intercooler is essential.

Fuel makes power, that is the biggest difference.

But air mass has to be supplied for an air/fuel ratio sufficiently over the smoke limit to keep egt under control. So matching a suitable turbo and intercooler for the required power level is required.

Originally Posted by Sparkie

Clean32,

That agrees with what i was told, but are you saying if you add a little more fuel it can counteract the extra advance by slowing the burn.
.

Not quite

Its a balancing act. You have burn before TDC and burn after TDC you want the bigger burn to be after TDC.

so ( I cant remember the numbers) some thing like this. 1X 500cc cylinder of air fuel once burnt = 1500 cubic meters of gas at ISO

By advancing the timing you produce a percentage of the total gas before TDC and a percentage after. Say for arguments sake 3% before and 97% after. by increasing the volume of air which is the same as increasing the compression ratio, the initial burn or the burn before TDC becomes more efficient ( regardless of if more fuel is pumped in or not)
So we end up with numbers like 10% before TDC and 90% after TDC

i know its an unrealistic scenario but you get the idea

If we take the first example 3% the 97% the first 3% of the post TDC burn is used to cancel out the pre TDC burn giving 94% for motivation. the second gives only 80% for motivation.

now if we start to add more fuel things become a bit more complicated.

where we have 10% And 90% we could end up with 12% and 88% add a bit more and we could come back to 10% and 90% a bit more fuel 5% and 95% etc then we get to a point where it will swing back the other way again as we keep adding more and more fuel.

as I said the numbers are not correct but it is just to paint a picture for you.


The pre burn that you refer to in comonrail motors is just that a bit of fuel to heat things up a bit before the big burn. makes the big burn much more efficient. back in the day we would run 2 injector pumps and injectors to get the same effect and before that we would run an electric single injector in the inlet manifold to get a bit of fuel in there first but this only worked at high revs

Originally Posted by Sparkie

...

Common rail engines inject a small amount early, so the main injection event burns almost immediately it is injected. ...

Not only common rail systems. Mechanical fuel injections systems can do this.

The Land Rover 300Tdi engine has 2 stage injectors for this feature.

Originally Posted by Sparkie

...

Bush65,

Should have been a little clearer about the advance numbers.

4BD1 13' static(crank) + 5' mechanical(pump) = 13 + (5*2) = 23' at 3000 rpm

4BD1T 10' static(crank) + 3.5' mechanical(pump) = 10 + (3.5*2) = 17' at 3000 rpm

Not sure how much difference 6 degrees would make or how much different the mechanical advance is on later engines. Would be interesting to find out.

Sparkie.

Thanks for clearing up where the value for 6 degrees difference came from - my manual has those same values for static timing and advance for the 4BD1 and 4BD1T, but I didn't look them up or do the sums.

I did a bit of reading (Diesel Engine Reference Book, 2nd ed), to see what the experts (Dr Jon Van Gerpen PhD PE & Dr Rolf Reitz PhD FSAE in the section that I took the following quote from (page 92)) say on timing vs boost pressure.

4.1.2 Ignition delay
Ignition delay is defined as the time period between the start of fuel injection and the start of combustion. As described earlier, the fuel must vaporize, mix with the air, and undergo preflame reactions before auto-ignition occurs. .... The temperature of the compressed air is the most important variable affecting ignition delay because it accelerates vaporization and the radical-forming preflame reactions. ....

Turbocharged diesel engines have very short ignition delays at full load but naturally aspirated engines and lightly loaded turbocharged engines can have ignition delays of 1-2 milliseconds. ....

...

Ignition delay is an important variable in diesel combustion because it has a strong correlation to the amount of fuel that is burned in the premixed combustion phase. Longer ignition delays allow more fuel to be injected and prepared for combustion. When ignition finally occurs, it involves more fuel and produces a violent autoignition, sometimes called diesel knock. In addition to being a source of undesirable noise, high levels of premixed combustion contribute to high nitric oxide (NO) levels in the exhaust. Experiments that sample the entire cylinder contents at different times during the combustion process have shown that NO is formed early and primarily from the products of the premixed combustion. This product gas is compressed by further combustion and gets to the highest temperature in the cylinder for the longest time. Recent results have shown that in highly turbocharged engines with late injection timing and very short ignition delays, less NO is formed and it is not necessarily associated with the first fuel to burn.

So there you go:
Less advance with turbo engines at full load because the ignition delay is shorter when the combustion air is hotter. (Edit) but apparently no great difference between lightly loaded turbo engines and NA engines. (end of edit)

And why common rail (and 2 stage mechanical injector) systems inject a small amount of fuel before the main injection - to reduce diesel knock and NO.

So is this why mine (non-wastegate intercooled)with a bit more fuel lowered the exh.temp then more fuel again up it goes,sort of fines a sweet spot of fuel,air temp and timing?

Originally Posted by yt110

So is this why mine (non-wastegate intercooled)with a bit more fuel lowered the exh.temp then more fuel again up it goes,sort of fines a sweet spot of fuel,air temp and timing?

yes, but i would have asumed that this was sorted on the dino, try backing the timing a couple of deg and up the fule again

Originally Posted by yt110

So is this why mine (non-wastegate intercooled)with a bit more fuel lowered the exh.temp then more fuel again up it goes,sort of fines a sweet spot of fuel,air temp and timing?

With your free float turbo, the boost pressure is determined by the amount of heat in the exhaust gas. Increasing the load and/or the fuel, will increase the heat in the exhaust and increase boost pressure.

The compressor has an operating region where it is most efficient, as the operating point moves to lower efficiency regions, it generates more heat in the compressed air for the particular air flow and the drive pressure at the turbine increases.

Increasing the air flow (usually associated with higher boost pressure), if it increases the air/fuel ratio will lower the egt.

However if the air/fuel ratio is lowered, the egt will rise.

what he said

the if is when you are trying to work out side the efficent envelope

Originally Posted by Bush65

With your free float turbo, the boost pressure is determined by the amount of heat in the exhaust gas. Increasing the load and/or the fuel, will increase the heat in the exhaust and increase boost pressure.

The compressor has an operating region where it is most efficient, as the operating point moves to lower efficiency regions, it generates more heat in the compressed air for the particular air flow and the drive pressure at the turbine increases.

Increasing the air flow (usually associated with higher boost pressure), if it increases the air/fuel ratio will lower the egt.

However if the air/fuel ratio is lowered, the egt will rise.

Originally Posted by Bush65

Stock, the full load and max speed screws have tamper proof shrouds.

If the pump goes to a diesel shop, they use wire and a lead seal on the screws to stop tampering.

Your turbo has a wastegate (some/most stock 4BD1T are free float), so you have both the wastegate, and the full load screws to adjust for boost pressure.

You have only mentioned adjusting the full load screw! Have you checked what pressure your wastegate is opening at?

Intercoolers don't help that much at low boost pressure.

Once you are over about 12 psi you may start to notice a difference if an intercooler is fitted. Some here are running much higher boost without an intercooler.

I am not saying they are not useful/helpful, just that you shouldn't think they will make a big difference at those levels of boost pressure. However if you run high fuel and boost pressure settings, a good intercooler is essential.

Fuel makes power, that is the biggest difference.

But air mass has to be supplied for an air/fuel ratio sufficiently over the smoke limit to keep egt under control. So matching a suitable turbo and intercooler for the required power level is required.

the waste gate was opening at 11psi, I have just fitted a turbosmart boost adjusting valve in the actuature hose and now at 14psi.

I would have thought a intercooler would be helping all the time of course more efficient at higher speeds and percentage wise greater reduction when temps are higher but if you have a means of cooling the intake temp it all has to help.

with common rail the last injection is a very small amount to reduce NOX, the last injection cools the combustion chamber enough to reduce the NOX for the emission standards.