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Throttle bodies vs carbs
- Thread starter SeanDezart
- Start date
STEVE BURNS
Club Member
how does it work
I'm not shy and not afraid to ask as it means nowt to me
I'm not shy and not afraid to ask as it means nowt to me
grolls
Well-Known Forum User
I knew some smart ass would respond to that!!!!!! and It had to be you!!!!!!STEVE BURNS said:how does it work
I'm not shy and not afraid to ask as it means nowt to me
I will try to put it in easy terms, so i shall type away and be back in a few...with mistakes no doubt
grolls
Well-Known Forum User
Injection systems need information to be able to work. The ECU (electronic control unit or brain if you like) needs to gather information from smaller items dotted about the engine. These are called sensors. They take readings from such things as how far your foot is depressed on the throttle (throttle position sensor) and Crank sensor(this takes a reading so when the ECU knows when the engine is at TDC) so just from these two a huge calculation can be made. For example if you are going up a very steep hill and you have your foot burried into the carpet and from the crank sensor it knows that the engine is not revoling fast enough it may advance/retard the timing or give more or less fuel as it needs according to the MAP that the ECU has. If you look at steves MAP, you should be able to see different loads under different condition.
There are obviously loads more sensors available to bolt on if needs be but this was just to give you an insight only and does in no way explain it 100% as I would be here for hours.
So effectivly we could say that it reads load v's demand v's economy v's performace but never v's looks
There are obviously loads more sensors available to bolt on if needs be but this was just to give you an insight only and does in no way explain it 100% as I would be here for hours.
So effectivly we could say that it reads load v's demand v's economy v's performace but never v's looks
Well it kind of goes like this.
In a typical carburettor, the air drawn into the engine on the induction stroke is accelerated over one or more venturi or jets, this then atomises the fuel which is usually pumped into the carb at around 3-5 psi, this air fuel mix is then drawn into the cylinder and ignited. This system has some drawbacks such as
1. Trying to tune carbs for all eventualities is nearly impossible and expensive, as you would need a lot of rolling road time and parts swapping,
2. In many performance carbs in order to get the airflow right, chokes are used to reduce the diameter of the mouth (speeds the air up) this results in reducing the available square area of the mouth and thus its volumetric flow.
3. Atomisation of fuel sometimes may be incomplete resulting in "globules" of fuel, which burn inconsistently and reduced power
Individual throttle body injection uses an adjustable, unrestricted throttle mouth per cylinder (no sharing here and 40mm is 40mm not 32 or 36 mm) high pressure fuel (around 45psi) is pumped through nozzles called injectors, 6 in this case, directly into the air flow to atomise the fuel giving a more uniform and controllable air fuel mixture. "So what" I hear you cry, well that’s only part of the story, injectors can be computer controlled so that they fire at exactly the right moment for exactly the right duration, whilst your at it you may as well get this fancy computer to do other things such as, vary the injector timing according to engine speed, air temp, density, water temp etc, all measured from sensors around the engine -- as the computer is still only ticking over, lets get it to manage the spark as well so the coils only fire when they should, avoiding the spark scatter of distributors.
So you end up with a fully computer managed system, the maps you see are the tables that the computer uses to look up a particular value at a particular load/speed, these maps are totally custom made (the one's you see are mine)
For example on the injection map at load site 15 and speed site 15 the injectors will be open for 120 "units" of time whilst at speed site 10 and load site 7 they are only open for 60 "units" ---- the longer/shorter the injectors fire, the more/less fuel is introduced into the air flow and the richer (or weaker) the mixture becomes -- et voila all of a sudden you have control.
So to sum up, the advantages of total engine management and individual throttle bodies are
1. Better (total) control of air fuel mix
2. Better atomisation of fuel at all air speeds, resulting in a better more controllable burn, hence more power, better economy and smoother running.
3. Control of fuelling/ignition under infinitely variable conditions
4. Elimination of spark scatter, resulting in higher achievable engine revs
5. Better cold weather starting
6. Better idle control
7. Computer control of cooling fan relative to system temps
8. Computer control of other ancillaries such as electric water pump, nitrous or traction control
9. Data logging for later analysis
10. Ability to self program, via lambda sensor
11. Hard and soft rev limiting
12. Knock sensing
13 Map switching (sport vs economy or test vs live maps)
The list goes on
In a typical carburettor, the air drawn into the engine on the induction stroke is accelerated over one or more venturi or jets, this then atomises the fuel which is usually pumped into the carb at around 3-5 psi, this air fuel mix is then drawn into the cylinder and ignited. This system has some drawbacks such as
1. Trying to tune carbs for all eventualities is nearly impossible and expensive, as you would need a lot of rolling road time and parts swapping,
2. In many performance carbs in order to get the airflow right, chokes are used to reduce the diameter of the mouth (speeds the air up) this results in reducing the available square area of the mouth and thus its volumetric flow.
3. Atomisation of fuel sometimes may be incomplete resulting in "globules" of fuel, which burn inconsistently and reduced power
Individual throttle body injection uses an adjustable, unrestricted throttle mouth per cylinder (no sharing here and 40mm is 40mm not 32 or 36 mm) high pressure fuel (around 45psi) is pumped through nozzles called injectors, 6 in this case, directly into the air flow to atomise the fuel giving a more uniform and controllable air fuel mixture. "So what" I hear you cry, well that’s only part of the story, injectors can be computer controlled so that they fire at exactly the right moment for exactly the right duration, whilst your at it you may as well get this fancy computer to do other things such as, vary the injector timing according to engine speed, air temp, density, water temp etc, all measured from sensors around the engine -- as the computer is still only ticking over, lets get it to manage the spark as well so the coils only fire when they should, avoiding the spark scatter of distributors.
So you end up with a fully computer managed system, the maps you see are the tables that the computer uses to look up a particular value at a particular load/speed, these maps are totally custom made (the one's you see are mine)
For example on the injection map at load site 15 and speed site 15 the injectors will be open for 120 "units" of time whilst at speed site 10 and load site 7 they are only open for 60 "units" ---- the longer/shorter the injectors fire, the more/less fuel is introduced into the air flow and the richer (or weaker) the mixture becomes -- et voila all of a sudden you have control.
So to sum up, the advantages of total engine management and individual throttle bodies are
1. Better (total) control of air fuel mix
2. Better atomisation of fuel at all air speeds, resulting in a better more controllable burn, hence more power, better economy and smoother running.
3. Control of fuelling/ignition under infinitely variable conditions
4. Elimination of spark scatter, resulting in higher achievable engine revs
5. Better cold weather starting
6. Better idle control
7. Computer control of cooling fan relative to system temps
8. Computer control of other ancillaries such as electric water pump, nitrous or traction control
9. Data logging for later analysis
10. Ability to self program, via lambda sensor
11. Hard and soft rev limiting
12. Knock sensing
13 Map switching (sport vs economy or test vs live maps)
The list goes on
SeanDezart
Well-Known Forum User
Errrhhhm.....Skiddy said it well "The L6 is bl**dy hard work (and expensive) to get good power out of" !
I think that to be getting 85bhp/litre from an L series is doing really, really good !
90+ on a race engine and I still have trouble accepting Mr Skiddells' 250 bhp from a 2.8, with or without TBs !
I prefer carbs 'cos they're cheaper; I like the look equally of them and TBs, if ever I do another car and Skiddy is getting 89+/litre plus great fuel economy and delivery, I shall be very tempted to go down the same way !
Fuel economy alone won't pay for the extra cost of TBs - we don't drive these cars 40,000 miles per year...do we ?
Ben, I accept that you use computer mapping but isn't it 'just' at the rolling road ? Skiddy does it everywhere, giving him a versatility (technological advantage) over yours !
And how much bhp do you expect to get / ltr (3.1 ?) ?
For the record, I'm expecting 270 from 3.1 on trilpe 45s, (87/litre) for a road car !
I think that to be getting 85bhp/litre from an L series is doing really, really good !
90+ on a race engine and I still have trouble accepting Mr Skiddells' 250 bhp from a 2.8, with or without TBs !
I prefer carbs 'cos they're cheaper; I like the look equally of them and TBs, if ever I do another car and Skiddy is getting 89+/litre plus great fuel economy and delivery, I shall be very tempted to go down the same way !
Fuel economy alone won't pay for the extra cost of TBs - we don't drive these cars 40,000 miles per year...do we ?
Ben, I accept that you use computer mapping but isn't it 'just' at the rolling road ? Skiddy does it everywhere, giving him a versatility (technological advantage) over yours
!And how much bhp do you expect to get / ltr (3.1 ?) ?
For the record, I'm expecting 270 from 3.1 on trilpe 45s, (87/litre) for a road car !
DJZ 60
Well-Known Forum User
I'm more than convinced about the pro's & con's in favour of TB's. Steve
you have beautifully presented a detailed account of how throttle bodies are
the evolutionary replacement for the older system.
One thing worries me a little...Say for example (& hypothethically
speaking) someone nicks your laptop/management system or for that matter
something fails on the electronic computer management system,then what?
I'm sure Sean would not like to be in that predicament,especially
when he is on the strip,& getting ready to show off his new motor.
Or say I'm doing a bank job(in my van) & the chipped management
system fail's as I try to speed off. Is there a back up to the management?
After this question,has been answered,I will proceed further & go
ahead with TB's,all inclusive of whatever's required & get my van done.
DJZ 60.
you have beautifully presented a detailed account of how throttle bodies are
the evolutionary replacement for the older system.
One thing worries me a little...Say for example (& hypothethically
speaking) someone nicks your laptop/management system or for that matter
something fails on the electronic computer management system,then what?
I'm sure Sean would not like to be in that predicament,especially
when he is on the strip,& getting ready to show off his new motor.
Or say I'm doing a bank job(in my van) & the chipped management
system fail's as I try to speed off. Is there a back up to the management?
After this question,has been answered,I will proceed further & go
ahead with TB's,all inclusive of whatever's required & get my van done.
DJZ 60.
ben240z
Club Member
sean the mapping was done on the dyno but there are a range of maps that I can load up or change to at meetings with the aid of the trusty laptop. This gives me the oportunity/versitility, of running less power in the wet for example. Add to that the different traction control maps that I can select for both wet and dry meetings and the data logging that the ECU is collecting all the time the engine is running, I am in the situation where the car can not really go out to race meetings without the laptop. The setup I use at the moment is that the ECU will store 12 minutes worth of data which can then be downloaded onto the laptop and examined at my leisure. However as I have said previously there is also the diagnostic facility in the system I am using to sort out any problems that occur. I am collecting data on many different fields eg, battery voltage, timing advance, injector pulse length and timing,throttle position, air temp, water and oil temp, engine rpm, wheel speed, to name but a few. This data is then downloaded after each competitive run and analysed to make sure that the car is running at the optimum setup. it also shows how the driver is performing because with throttle position, RPM, wheel speed you can work out how long the driver is, braking for a corner, is taking to change gear, and how consistant they are driving. When you are looking to gain hundreths of a second for example then you need to know where you can make up time by braking later or changing gera quicker,sooner or even holding a gear longer and saving a gear change. Unlike drag racing we run in the wet as well as the dry therefore if the engine is as drivable as a standard 240 road engine with it's power delivery( I can make it even more docile if needed) then could this possibly be a slight advantage over a tail happy, smile inducing carbed 240Z. I can only answer that for myself but maybe if you had that technology then you car would not have ended up in a field when you took cathy out in it!!!!!!!! Please feel free to come and have a look at the car at any time(this offer is open to all, I have nothing to hide) I hope to be out more this year with the car, even over to your neck of the woods.
ben240z
Club Member
dj, the ECU is as reliable as the ECU that are running road cars now. If they pack up you replace it. I would suggest that for the bank job you stick to a car with points and a condenser that way if the engine fails to start you can always clean and adjust the points. If someone nicks the laptop then you hit them hard and use another one. The system I am using is popular in the hillclimb paddock so there are plenty of other laptops that you could borrow to tweek the ECU with. I also carry a disc with all maps and data on for that reason.
ZHead
Well-Known Forum User
Can I throw a spanner in the works guys ? (You would expect nothing less)
What would happen if you were to use carbs as the fuel delivery system but used ECU mapped ignition ?
From a cost perspective it would not save any money at all but from an aesthetic point of view you would have triples, glorious induction roar (albeit hot air) and mappable ignition to get the timing just right.
I accept that you would lose the flexibility of quick map changes but would it work for say one specific set up ?
What would happen if you were to use carbs as the fuel delivery system but used ECU mapped ignition ?
From a cost perspective it would not save any money at all but from an aesthetic point of view you would have triples, glorious induction roar (albeit hot air) and mappable ignition to get the timing just right.
I accept that you would lose the flexibility of quick map changes but would it work for say one specific set up ?
SeanDezart
Well-Known Forum User
"a tail happy, smile inducing carbed 240Z" - I expect my car to not at all be tail happy - just quick and I do understand your phraseology and I expect to have a smile !
I take back therefore what I said about technology etc and look forward to swapping cars for a run
Yes, I know 100/litre has been acheived, Daves' old modsports car with a 3.1 was producing 310 + ON CARBS !
My point was for road cars, it's not so easy to produce a driveable (for the road) engine producing more than 85/litre !
I take back therefore what I said about technology etc and look forward to swapping cars for a run
Yes, I know 100/litre has been acheived, Daves' old modsports car with a 3.1 was producing 310 + ON CARBS !
My point was for road cars, it's not so easy to produce a driveable (for the road) engine producing more than 85/litre !
ben240z
Club Member
I havnt noticed that the glorious induction roar has gone There are still 6 big holes for the air to roar through. Has your engine got quiter steve?????????
sean if you are going to split road cars from race cars then what is the point of having all that extra horsepower. you cant use it on the road, its just a waste of money. stick with a standard engine. now if you take a left turn and say well your car is going to be a track car as well then it is not a road car so therefore the 100hp/ltr rule should apply. And you are still confusing an engine as a road or race going item. My engine, steves engine would drop into a road standard car and still be more drivable than a standard engine because of the power delivery. The engine in my car is merely the power plant. The other items it is attached to make it a race car, ie the straight cut close ratio gearbox (5th gear is not even 1:1) sourced purely for the hillclimb. The 3:1 to 1 diff. The lightweight shell etc this is what makes it a race car
sean if you are going to split road cars from race cars then what is the point of having all that extra horsepower. you cant use it on the road, its just a waste of money. stick with a standard engine. now if you take a left turn and say well your car is going to be a track car as well then it is not a road car so therefore the 100hp/ltr rule should apply. And you are still confusing an engine as a road or race going item. My engine, steves engine would drop into a road standard car and still be more drivable than a standard engine because of the power delivery. The engine in my car is merely the power plant. The other items it is attached to make it a race car, ie the straight cut close ratio gearbox (5th gear is not even 1:1) sourced purely for the hillclimb. The 3:1 to 1 diff. The lightweight shell etc this is what makes it a race car
SeanDezart
Well-Known Forum User
What is the point in having all that extra horse-power ? Because I canben240z said:
Ask any hybridz man why he's going for 300bhp + ! And of course I can use it on the road - not yours, they're too full and I will make use of open circuit days and if Skiddy pays for the burgers and fries, I'll do a drag-strip or two Errr, the engine is also the race car, not merely anything - attach all those sporty bits to a std engine and win ! And yes, mine will have certain 'race bits' but is still a road car, comfortable, music, sound-proofed (ish).
ben240z
Club Member
so if we were to drop my engine into your road car would that make your road car a race car or my engine a road engine?
I have music in my car, it's the glorious sound of the induction roar and the engine
I have sound proofing in my car, it's called a crash helmet
My car is comfortable
so all that makes it a road car
one day this roundabout is going to go so fast that we are all going to fall off.
I will provide the burgers and beer when you do a drag meet. All we got to do is find a meet that we can all get to.
I have music in my car, it's the glorious sound of the induction roar and the engine
I have sound proofing in my car, it's called a crash helmet
My car is comfortable
so all that makes it a road car
one day this roundabout is going to go so fast that we are all going to fall off.
I will provide the burgers and beer when you do a drag meet. All we got to do is find a meet that we can all get to.
SeanDezart
Well-Known Forum User
And my car has a number plate, inertia reel seatbelts and conforms to road laws - it's a road car with a road engine But it'd give you a fright Ben, what do they drink with burgers down in Somerset ?
But it'd give you a fright Ben, what do they drink with burgers down in Somerset ?
SeanDezart
Well-Known Forum User
Yours' is not only bigger, it's heavier, more like sag what you brought !