Defender 90 TD5 - Remapped. Power issues beyond 65mph

ozzyboydeano said:

this is where the MAP sensor comes to play ..this is the last map to tell the ecu what to do it lets the ecu know how much boost pressure as well has intake air temp

as for heat research how a turbo works !
hot gasses expand this is what pushed the turbine
to make boost you need fuel and air more fuel more air more boost

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johnlad said:

In my mind its the flow of gas through the exhaust which spins the turbo, not how hot the gas is, the heat is a by product of the turbo working and is best reduced as much as possibe, which is the reason bigger intercoolers are used, as they lower the intake air temp, as cold air is denser it produces more power

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ozzyboydeano said:

you are confused with the hot and cold side of a turbo but you are correct cooling charged air
try this link below it a basic read up but will explain it better than I can type ... the correct words are kinetic and thermal energy
there are 2 sides to a turbo hot side and cold side.. to make boost you need heat in the hot side of the turbo


if you really think that its exhaust flow .install a boost gauge
rev engine in neutral to 2000 or 3000 rpm you might make 2 to 3 psi boost pressure the reason being there is no engine load .no engine load means less fuel means lower EGT in return no boost pressure

http://www.epi-eng.com/piston_engine_technology/turbocharger_technology.htm

this is why some turbo people like to install turbo blankets AKA turbo socks to contain the heat on the hot side of the turbo https://www.google.com.au/search?q=turbo+sock&biw=1093&bih=522&tbm=isch&imgil=HFQNNpj537lXIM%3A%3BgD75jdc2E_q8fM%3Bhttp%253A%252F%252Fwww.duramaxdiesels.com%252Fforum%252Fshowthread.php%253Ft%25253D23046&source=iu&pf=m&fir=HFQNNpj537lXIM%3A%2CgD75jdc2E_q8fM%2C_&usg=__rsw_R7x1IrCOnybTJ6dU3eqaV1M=&ved=0ahUKEwi6svLUjYrRAhXBS7wKHcV8CvoQyjcIMg&ei=a_xcWPrQE8GX8QXF-anQDw#imgrc=HFQNNpj537lXIM:

basically hot side contain the heat ..cold side lower charge temps

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Gottschalk said:

So get off your high horse and read my reply, I didn't bother looking at any of the links you posted as the answer is pretty obvious

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ozzyboydeano said:

so if its exhaust flow
how come I can only make 1 nearly 2 psi boost pressure when revving my engine 2000 rpm in neutral (can prove it )
.

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ozzyboydeano said:

I do apologise if I have offended you
but its actually a known fact
reason you don't want to open the links because you will have to accept that your wrong .no one likes to be wrong

so if its exhaust flow
how come I can only make 1 nearly 2 psi boost pressure when revving my engine 2000 rpm in neutral (can prove it )
.
as for the cold side of the turbo yes cooling the air is best reason why they come out from factory with a intercooler

but the hot side of the turbo works different to the cold side

hopefully some members with boost gauges installed notice they make boost down low ..rather than high rpm

I love when people come in and want more boost use less fuel ..but they do not understand how a turbo works because they want 40 psi like they seen a vid on youtube or social media LOL

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Gottschalk said:

Basically johnlad and bankz are totally correct. The turbo spins up from the flow of exhaust gases passing through it. The fact that this is hot air is nothing to do with anything turbo wise, exhaust gases are always hot!
If you put a straight through pipe on a mapped td5 you will notice the turbo spools up much faster, and lower down the revs, that's because the gases are unrestricted and are spinning the turbo up faster.

The turbos JOB is to force the cold dense air into the cylinder, and this occurs from the FLOW of exhaust, not the temperature of it

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ozzyboydeano said:

I do apologise if I have offended you
but its actually a known fact
reason you don't want to open the links because you will have to accept that your wrong .no one likes to be wrong

so if its exhaust flow
how come I can only make 1 nearly 2 psi boost pressure when revving my engine 2000 rpm in neutral (can prove it )

Id imagine the reason you have little boost whilst stationary or not under load is because the wastgate is open.

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1. The wastegate: this is a valve that also sits in the exhaust gas path. It provides a short cut for the exhaust if the engine does not really need boost at this time. This can be used for peak boost control (too much boost can physically destroy your engine). This can be a purely mechanical sprung valve that stays closed up to a certain positive pressure in the intake path and then progressively opens as boost increases. It could also be under the direct control of the engine computer. For example, my car (in stock tune) was very annoying in its refusal to stay at peak boost in third gear. It also would refuse to boost past a certain point with partial throttle. The engine computer was effectively saying "no, that's enough fun for now."
   

jamesmartin said:

in theory if hot gasses were to be suddenly cooled by a cold turbo it would lose some of its force but you wouldnt notice the fractional loss on a landrover or average car, straight through pipe though does make a noticeable difference

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bankz5152 said:

I may be wrong but isnt EGT an indicator of air - fuel ratio?

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johnlad said:

1. The wastegate: this is a valve that also sits in the exhaust gas path. It provides a short cut for the exhaust if the engine does not really need boost at this time. This can be used for peak boost control (too much boost can physically destroy your engine). This can be a purely mechanical sprung valve that stays closed up to a certain positive pressure in the intake path and then progressively opens as boost increases. It could also be under the direct control of the engine computer. For example, my car (in stock tune) was very annoying in its refusal to stay at peak boost in third gear. It also would refuse to boost past a certain point with partial throttle. The engine computer was effectively saying "no, that's enough fun for now."

For example, if I am rolling downhill in gear with my foot off the gas, the throttle is closed. There isn't enough air mass passing through the intake to exhaust path to make the turbo spin, wastegate or not.

However, the scene changes at the bottom of the hill as we climb the next rise. I have to open the throttle to get up the hill. If I'm in low gear, the RPMs will be higher, the exhaust gas energy will be higher and the turbine will spin right up. However, since I'd require partial throttle at lower gear for the same acceleration, my engine computer might veto boost past a certain point, opening the wastegate.

If I'm in high gear, the RPMs will be lower and I'll have to open the throttle wide open to get up the hill. However, the exhaust gas volume and velocity will be low and it's possible that I won't have enough energy for the turbo to make any significant positive pressure (e.g., around 40 mph in fifth in my car). Even though I'd really like to make boost in this situation, I won't be able to.

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