Improved Fuel Economy from "Added" Low-Pressure Turbo

[Veloc]

Hi guys... New cars with low-pressure turbo (LPT) especially the european ones have ever increasingly fuel efficiency and economy. They don't give much high end power compared to high-pressure turbos, but surely loads of low end torque for strong low to mid range acceleration, which is... quite fun. The principle is simple, more torque allows you to accelerate to the cruising speed faster and thus it reaches the higher gears faster. More torque also enables taller gearing.

Now the question is... Is there anybody who did a bolt-on turbo (BOT) / self-modified turbo to their stock NA car and achieve similar result (improved fuel economy)? Please share on the type, settings, location or anything info.

---------- Post added at 02:37 AM ---------- 6 hour anti-bump limit - Previous post was at 02:33 AM ----------

Usually, BOT engines are more thirsty due to the ECU that is not originally designed for boost. Improved economy is only gained if the car have early boost around 1.5k rpms and maximum vacuum while cruising. Maximum vacuum when cruising is the most important for good FC. Most BOT do not have an engine management/piggyback that can release boost to create vacuum for economical cruising. Even is the throttle is almost closed during cruising, there is still a certain degree of boost that exist. So BOT generally have worse FC. Now the question is... Is there such a boost controller/engine management/piggyback unit that can help to release the boost when the car is cruising? Can a systems sense that a car is cruising and not accelerating and thus opens the wastegate to prevent boosting? If there is such a system, better FC from BOT can be achieved!
Please share!

 

[hachiroku clan]

i was thinking about that too, but i never came across a guy who adds turbo for 'fuel economy' YET.. futhermore, there are other ways of saving fuel rather than bolting a turbo on a non-turbo cars.. even if it does, it might take years to pay off the cost of bolting the turbo ..

same case of the toyota prius, people are asking is it worth it to buy an expensive hybrid for the sake of fuel economy? taking into consideration the cost of the battery, etc, it takes years for the owner to actually save some money on fuel..

this makes me wonder, is the new campro turbo /phoenix engine is designed for performance or fuel economy? or both?

 

[speed2horizon]

Hi guys... New cars with low-pressure turbo (LPT) especially the european ones have ever increasingly fuel efficiency and economy. They don't give much high end power compared to high-pressure turbos, but surely loads of low end torque for strong low to mid range acceleration, which is... quite fun. The principle is simple, more torque allows you to accelerate to the cruising speed faster and thus it reaches the higher gears faster. More torque also enables taller gearing.

Now the question is... Is there anybody who did a bolt-on turbo (BOT) / self-modified turbo to their stock NA car and achieve similar result (improved fuel economy)? Please share on the type, settings, location or anything info.

---------- Post added at 02:37 AM ---------- 6 hour anti-bump limit - Previous post was at 02:33 AM ----------

Usually, BOT engines are more thirsty due to the ECU that is not originally designed for boost. Improved economy is only gained if the car have early boost around 1.5k rpms and maximum vacuum while cruising. Maximum vacuum when cruising is the most important for good FC. Most BOT do not have an engine management/piggyback that can release boost to create vacuum for economical cruising. Even is the throttle is almost closed during cruising, there is still a certain degree of boost that exist. So BOT generally have worse FC. Now the question is... Is there such a boost controller/engine management/piggyback unit that can help to release the boost when the car is cruising? Can a systems sense that a car is cruising and not accelerating and thus opens the wastegate to prevent boosting? If there is such a system, better FC from BOT can be achieved!
Please share!

Well, just to share my shallow knowledge on BOT. Ur car will be automatically runs on vacumn without any management control when air consumption is higher than ur boost created. This is a normal characteristic of our engines regardless of turbocharged or not. Except for supercharged engines.

Even on 50% throttle position, if the load is low. Car will still be running at vacumn. This happens whenur engine is on cruise. However, low pressure turbo are turbos that have a low effective pressures at low cfm. That u can check from the turbine and compressor mapping on the turbo spec sheet.

Regarding, the fuel economy part. It's all about tunning. On a dyno machine, u'll expect to extract the maximum hp out of the engine. However, we tends to ignore the low end and the cruising part of the entire afr map. I have my emanage tuned on road with wideband attached on the exhaust. Knowing the engine is running at low compression pistons, I've
tuned my low 500rpm-1000rpm at TP
Also knowing that my turbo kicks in at 3000rpm at TP>30%, I've tuned to achieve 12-13. currently boosting at 0.7 bar.

My fuel consumption improved from 430km to 480-530km. That's because most of the time, our car will be running at either cruise or got stucked in the traffic jam and street spirited driving once anwhile.. And that's why I got it tuned that way.

So, am I considered success BOT that improves fuel consumption??? Haha...

 

[xtremeleo]

after changing to a 1.3liter charged engine, i got better FC compared to my previous 1liter. dat 1liter was in good shape fyi, but the tuning state and torque value is better on the new engine hence the better FC.

for a bot project, i dont see y the fc shudnt get any better, if driven sensibly ler..

 

[Veloc]

i was thinking about that too, but i never came across a guy who adds turbo for 'fuel economy' YET.. futhermore, there are other ways of saving fuel rather than bolting a turbo on a non-turbo cars.. even if it does, it might take years to pay off the cost of bolting the turbo ..

same case of the toyota prius, people are asking is it worth it to buy an expensive hybrid for the sake of fuel economy? taking into consideration the cost of the battery, etc, it takes years for the owner to actually save some money on fuel..

this makes me wonder, is the new campro turbo /phoenix engine is designed for performance or fuel economy? or both?

I don't think the fuel savings from prius can offset its high price. The price is 176k. Higher than camry here in Kota Kinabalu. And my friend got 1000km per full tank. But have to cost in the battery periodical maintenance again... Actually it doesn't cost that much. Prius is a budget car in the US. Only the stupid gov taxed the hell out of us.

And about the BOT for good FC, yes very few people would consider such option if they have fuel economy in mind... but I'm one of those crazy ones LOL... And it is achievable. About whether the savings can pay off the cost of modification? I don't l know... Maybe takes a long time... But my aim is not to collect back the money spent. I just want to spend the money at once and get better power, torque, and FC over my period of using the car ^^.

---------- Post added at 02:51 PM ---------- 6 hour anti-bump limit - Previous post was at 02:45 PM ----------

Well, just to share my shallow knowledge on BOT. Ur car will be automatically runs on vacumn without any management control when air consumption is higher than ur boost created. This is a normal characteristic of our engines regardless of turbocharged or not. Except for supercharged engines.

Even on 50% throttle position, if the load is low. Car will still be running at vacumn. This happens whenur engine is on cruise. However, low pressure turbo are turbos that have a low effective pressures at low cfm. That u can check from the turbine and compressor mapping on the turbo spec sheet.

Regarding, the fuel economy part. It's all about tunning. On a dyno machine, u'll expect to extract the maximum hp out of the engine. However, we tends to ignore the low end and the cruising part of the entire afr map. I have my emanage tuned on road with wideband attached on the exhaust. Knowing the engine is running at low compression pistons, I've
tuned my low 500rpm-1000rpm at TP
Also knowing that my turbo kicks in at 3000rpm at TP>30%, I've tuned to achieve 12-13. currently boosting at 0.7 bar.

My fuel consumption improved from 430km to 480-530km. That's because most of the time, our car will be running at either cruise or got stucked in the traffic jam and street spirited driving once anwhile.. And that's why I got it tuned that way.

So, am I considered success BOT that improves fuel consumption??? Haha...

Haha... Sorry for being noob ya... But what is "cfm"? And what is "wideband"?

Oh ya... And why don't you tune the AFR to about 15:1 during cruise (3000-6000rpm at TP
and is it okay to run at 15:1 at 500rpm-1000rpm at TP
And btw, thank you for your info on throttle position, engine load and vacuum! So you are saying that the vacuum automatically generates during light load cruising right? If I get you right... Thank you!

 

[jinkl]

let me give this a shot , correct me if im wrong, im a newbie :P

turbocharging in current era is not the same as how it was those days
these days fuel efficiency is not played by Turbocharger only

wht is combo'd together with it tht creates power and fuel economy

1. High Compression Ratio, Soft turbo
2. Direct injection GDI
3. Leaner AFR but retaining power and reliability , engine design
4. Gearbox ratios redifined , more shorter gears but more gears, 6 speed ? 7 speed
5. VNT / VGT Turbochargers, variable turbocharger like the ones equiped in the Audi's , Peugeot , Porshe , VW , Mercedes, they all run on variable geometry turbos , this affects efficiency by alot more, there is no place for lag , no place for waits , no chokes , variable is intech
6. Engine head design, we are still sticked on to "Mivec" and "Vtec" , the world has already gone to
Alfa Twin Spark , BMW Double Vanos , Fiat VIS , Ford VCT , i-vtec , a-vtec , Porshe Vario , Volvo CVVT , even proton is on CPS :D , so the world of head has evolved
7. Electronics , ecu and closed loop technology - those days not all cars are equiped with wideband o2 sensors , air temperature sensors , barometric sensors , these are technologies that improve fuel economy

so in other words , jst the turbocharger without technology would yield u better fc :)

 

[Veloc]

let me give this a shot , correct me if im wrong, im a newbie :P

turbocharging in current era is not the same as how it was those days
these days fuel efficiency is not played by Turbocharger only

wht is combo'd together with it tht creates power and fuel economy

1. High Compression Ratio, Soft turbo
2. Direct injection GDI
3. Leaner AFR but retaining power and reliability , engine design
4. Gearbox ratios redifined , more shorter gears but more gears, 6 speed ? 7 speed
5. VNT / VGT Turbochargers, variable turbocharger like the ones equiped in the Audi's , Peugeot , Porshe , VW , Mercedes, they all run on variable geometry turbos , this affects efficiency by alot more, there is no place for lag , no place for waits , no chokes , variable is intech
6. Engine head design, we are still sticked on to "Mivec" and "Vtec" , the world has already gone to
Alfa Twin Spark , BMW Double Vanos , Fiat VIS , Ford VCT , i-vtec , a-vtec , Porshe Vario , Volvo CVVT , even proton is on CPS :D , so the world of head has evolved
7. Electronics , ecu and closed loop technology - those days not all cars are equiped with wideband o2 sensors , air temperature sensors , barometric sensors , these are technologies that improve fuel economy

so in other words , jst the turbocharger without technology would yield u better fc :)

True... True... Of course all those are out of our leagues la... But I just want to try doing what that still an be done and LPT is one of it... The effect won't be as great as all those combos however... Just looking for some fun/torque without sacrificing much on fuel price >.^

 

[xtremeleo]

who is dis noob jinkl laa? doesnt sound like a noobie pun, hehe..

ehh, whazzat? post.. 3,765????!!!!!

 

[jinkl]

True... True... Of course all those are out of our leagues la... But I just want to try doing what that still an be done and LPT is one of it... The effect won't be as great as all those combos however... Just looking for some fun/torque without sacrificing much on fuel price >.^

really depends on ur car actually and what engine you are running
a small turbo , with low boost , o2 sensor and air temp sensor in good condition
a good tune up will do well :)

believe or not , t04e , 4g63 2.0 , went to melaka n came back with rm30 wakakakakaka

 

[speed2horizon]

I don't think the fuel savings from prius can offset its high price. The price is 176k. Higher than camry here in Kota Kinabalu. And my friend got 1000km per full tank. But have to cost in the battery periodical maintenance again... Actually it doesn't cost that much. Prius is a budget car in the US. Only the stupid gov taxed the hell out of us.

And about the BOT for good FC, yes very few people would consider such option if they have fuel economy in mind... but I'm one of those crazy ones LOL... And it is achievable. About whether the savings can pay off the cost of modification? I don't l know... Maybe takes a long time... But my aim is not to collect back the money spent. I just want to spend the money at once and get better power, torque, and FC over my period of using the car ^^.

---------- Post added at 02:51 PM ---------- 6 hour anti-bump limit - Previous post was at 02:45 PM ----------



Haha... Sorry for being noob ya... But what is "cfm"? And what is "wideband"?

Oh ya... And why don't you tune the AFR to about 15:1 during cruise (3000-6000rpm at TP
and is it okay to run at 15:1 at 500rpm-1000rpm at TP
And btw, thank you for your info on throttle position, engine load and vacuum! So you are saying that the vacuum automatically generates during light load cruising right? If I get you right... Thank you!

Cfm is a measurement of flow. Cubic feet per minute is the unit.

Wideband aka wideband O2 sensor aka platinum type O2 sensor is another type of o2 sensor which gives 0-1V signal. Precise afr reading of 8-22(can be set to higher range).

Comparing to mostof the stock Oem O2 sensor which is aka narrowband o2 sensor aka zirkonium type O2 sensor which only reads lean, psychiometric or rich. But it won't gives u the exact afr reading Which is required and necessary when tunning.

Back to the question, when ur engine is on high revolution, ur pistons and cylinders will encounter alot of heat and friction. With a lean afr, then
will tends to heat up more than idle. The temperature of the cylinder will inrease the possibility of premature detonation. So it's risky to have a lean afr. And also, at 3000rpm, which is the effective spools in rpm for my turbo, a little increment in tps will cause increment in boost too. So, there's a second risk.

But my enginenis running on lower compression ratio, so when iddling(500-1500) rpm and lo load
Hope this help.

 

[jinkl]

"The engine management system continually chooses among three combustion modes: ultra lean burn, stoichiometric, and full power output. Each mode is characterized by the air-fuel ratio. The stoichiometric air-fuel ratio for petrol (gasoline) is 14.7:1 by weight, but ultra lean mode can involve ratios as high as 65:1 (or even higher in some engines, for very limited periods). These mixtures are much leaner than in a conventional engine and reduce fuel consumption considerably."

Gasoline direct injection - Wikipedia, the free encyclopedia

new I-Vtec-I
just for some info
AFR up to 65:1
http://paultan.org/2007/04/18/hondas-i-vtec-i-engine-direct-injection/

 

[Veloc]

"The engine management system continually chooses among three combustion modes: ultra lean burn, stoichiometric, and full power output. Each mode is characterized by the air-fuel ratio. The stoichiometric air-fuel ratio for petrol (gasoline) is 14.7:1 by weight, but ultra lean mode can involve ratios as high as 65:1 (or even higher in some engines, for very limited periods). These mixtures are much leaner than in a conventional engine and reduce fuel consumption considerably."

Gasoline direct injection - Wikipedia, the free encyclopedia

new I-Vtec-I
just for some info
AFR up to 65:1
http://paultan.org/2007/04/18/hondas-i-vtec-i-engine-direct-injection/

Nice! What beautiful innovation by Honda!

---------- Post added at 06:29 PM ---------- 6 hour anti-bump limit - Previous post was at 06:29 PM ----------

Cfm is a measurement of flow. Cubic feet per minute is the unit.

Wideband aka wideband O2 sensor aka platinum type O2 sensor is another type of o2 sensor which gives 0-1V signal. Precise afr reading of 8-22(can be set to higher range).

Comparing to mostof the stock Oem O2 sensor which is aka narrowband o2 sensor aka zirkonium type O2 sensor which only reads lean, psychiometric or rich. But it won't gives u the exact afr reading Which is required and necessary when tunning.

Back to the question, when ur engine is on high revolution, ur pistons and cylinders will encounter alot of heat and friction. With a lean afr, then
will tends to heat up more than idle. The temperature of the cylinder will inrease the possibility of premature detonation. So it's risky to have a lean afr. And also, at 3000rpm, which is the effective spools in rpm for my turbo, a little increment in tps will cause increment in boost too. So, there's a second risk.

But my enginenis running on lower compression ratio, so when iddling(500-1500) rpm and lo load
Hope this help.

Alright! Thanks for info!

---------- Post added at 06:32 PM ---------- 6 hour anti-bump limit - Previous post was at 06:29 PM ----------

really depends on ur car actually and what engine you are running
a small turbo , with low boost , o2 sensor and air temp sensor in good condition
a good tune up will do well :)

believe or not , t04e , 4g63 2.0 , went to melaka n came back with rm30 wakakakakaka

Small... 1.6L 4AFE... thinking of a few options for future...

1. Turbo it but remain economical...
2. Plonk in Blacktop 20V
3. Plonk in Blacktop 20V and turbo the thing
4. Put in a 3S-GTE and convert to 4wd (At this stage, can kiss Fuel Economy Goodbye)

 

[Big[V]]

BOT depending on size of turbo and engine configuration will have different RPM points when manifold starts to intersect 0 boost. Anything under that intersect RPM point would mean the MAP sensor will read vacuum as the exhaust gas flow is too low to spool any positive boost from the compressor.

Generally internal combustion engine requires 14.7 part air to 1 part fuel for complete combustion.

If manifold reads partial vacuum at cruise lets say 0.8 atm, by VOLUME it also means 14.7:0.8 AFR. In other iterations it is 18.375:1 AFR. Many economy engines can do this.

In other words, the physical volume of fuel injected at 0.8 atm is less than when the manifold is at 1 atm.

lower manifold pressure = Less fuel injected = less power = better mileage

If in N/A form if you change the intake runner to a more free flow type you'd probably reduce the manifold vacuum as it breaths better. Top end power will benefit but since manifold vac is reduced at low revs should also means mileage deficit during cruising.

If in turbo form the manifold vac during cruise could be more than N/A due to the additional restriction from the compressor itself.

Even so, any stock vehicle ecu setting would have slightly richer fuel setting for added safety margin.

By ecu tuning the whole setup can be optimized and IMO is where you can improve mileage the most.

Just my 2 cents. I stand corrected but anyway this is my understanding.

 

[xtremeleo]

i still believe its down to ur driving style, bot or not, high comp charged engine or na, if ur right leg doesnt know to lighten up, den d fc is still gonna suffer

 

[Newbienissan]

after changing to a 1.3liter charged engine, i got better FC compared to my previous 1liter. dat 1liter was in good shape fyi, but the tuning state and torque value is better on the new engine hence the better FC.

for a bot project, i dont see y the fc shudnt get any better, if driven sensibly ler..

i believe, if the BOT is tuned to focus to boost as low as 2800rpm-4000rpm, what really helps you safe petrol is u get a smooth power without changing to lower gear n pull up to higher rpm. it eliminate less vibration n noise. that is why those soft-turbo is equipt in continental cars, for more quite but torqueir at low rpm, not for performance driving.

 

[Big[V]]

Most engines' optimum brake specific fuel consumption is between 2000 to 3000 rpms. In other words, the motors efficiency will be at its optimum around that rev range. Anything higher the benefits will be cancelled out due to wind resistance.

Low boost turbo equipped cars like the VW Golf 1.4 TSI single turbo focuses on low rev range driveability. It's peak torque is available as low as 1700 rpms. Peak power is at modest 90kW.

During cruise/no boost the 1.4L motor delivers good mileage as it is but it's tiny turbo is fast enough to respond and delivers ample torque for acceleration.

 

[jswong]

But one of the reasons why factory-turbo'd European cars achieve such good fuel economy is because the transmission ratios are selected to take advantage of the higher torque. An NA engine might be doing 2800 rpm to hit 110km/h in top gear, but for a turbocharged car the gear ratios could be different, allowing the engine to spin at only 2400 rpm, for instance. So, despite the higher fuel-air charge density due to the turbo, the engine's producing a higher torque spread across the rev range. This higher torque is being exploited with taller gearing, and we end up with better FC.

If a regular car is fitted with BOT, we're still working with the stock standard gear ratios, so our FC improvements would still be somewhat limited.

 

[Veloc]

BOT depending on size of turbo and engine configuration will have different RPM points when manifold starts to intersect 0 boost. Anything under that intersect RPM point would mean the MAP sensor will read vacuum as the exhaust gas flow is too low to spool any positive boost from the compressor.

Generally internal combustion engine requires 14.7 part air to 1 part fuel for complete combustion.

If manifold reads partial vacuum at cruise lets say 0.8 atm, by VOLUME it also means 14.7:0.8 AFR. In other iterations it is 18.375:1 AFR. Many economy engines can do this.

In other words, the physical volume of fuel injected at 0.8 atm is less than when the manifold is at 1 atm.

lower manifold pressure = Less fuel injected = less power = better mileage

If in N/A form if you change the intake runner to a more free flow type you'd probably reduce the manifold vacuum as it breaths better. Top end power will benefit but since manifold vac is reduced at low revs should also means mileage deficit during cruising.

If in turbo form the manifold vac during cruise could be more than N/A due to the additional restriction from the compressor itself.

Even so, any stock vehicle ecu setting would have slightly richer fuel setting for added safety margin.

By ecu tuning the whole setup can be optimized and IMO is where you can improve mileage the most.

Just my 2 cents. I stand corrected but anyway this is my understanding.

Thank you! That was well explained... I never thought of the extra restriction by the turbo could actually increase vacuum a little.

 

[nakamichi]

I use to owned a 4G92 BOT with TD05 and 4G91 gearbox, FC very good... can run for 480 - 500km for a tank petrol...

regards.

 

[Big[V]]

Thank you! That was well explained... I never thought of the extra restriction by the turbo could actually increase vacuum a little.

For NA cars just use smaller diameter intake runner. It does 2 things:

1. Increased charged air velocity with smaller diameter intake to promote better air fuel mixture and increase negative manifold pressure.

2. Will suffocate sooner than stock intake runner meaning top end power will suffer.