one last question-keep the air mass meter or not?
Discussion
hi all,firstly,thanks for answering my previous questions regarding ignition choices etc.i now have one more choice to make before having my omex 700 system fitted next month.i dont know weather to keep and use the amm or not.apparently there are certain advantages for loosing the amm,slow feedback signal speed?(dont know any others)but ive also heard of good reasons for keeping it,ie its very accurate,it takes into account engine wear etc.so im wondering which i should do.will it really make that much more power/torque without it?my griff 500 is modified to v8d stage 3 induction package,ill be running pair fired injectors,original lambda sensors(maybe just one,any advice on this also welcome!))and the ignition mapped through distributor(crank triggered).all advice greatefully received as ever,cheers,mike v.
Paired, batch, same thing. Its just how they are connected to the ecu, not necessarily how they are fired.
The inj on my DTA are wired in the same way for group fire.
4 inj outputs, attached to 8 inj.
Id be surprised if the Omex has teh ability to read an airflow meter ?
If it was me, I'd ditch it.
The inj on my DTA are wired in the same way for group fire.
4 inj outputs, attached to 8 inj.
Id be surprised if the Omex has teh ability to read an airflow meter ?
If it was me, I'd ditch it.
Mongoose,
How fast will you wear your engine out?
Peter, batch fire, bank fire or group fire basically means pulsing the injectors in groups 2 times per cycle as oposed to sequential injection which pulses each injector once per cycle. I think sequential is an emmissions thing, batch fire saves you having to buy larger injectors. Some engines are sequential at low rpms and batch further up the rev range.
Boosted.
How fast will you wear your engine out?
Peter, batch fire, bank fire or group fire basically means pulsing the injectors in groups 2 times per cycle as oposed to sequential injection which pulses each injector once per cycle. I think sequential is an emmissions thing, batch fire saves you having to buy larger injectors. Some engines are sequential at low rpms and batch further up the rev range.
Boosted.
I was wondering whether paired firing was some cute trick to avoid the inherent asymmetry of bank fired injectors (i.e. the fuel is injected at a different phase of the firing cycle for each cylinder) without requiring a cam phase sensor. Might be a neat combination with wasted spark? No idea whether it would work, just intrigued by the idea.
Boosted LS1 said:must admit,thats how i was thinking!hopefully not THAT fast
Mongoose,
How fast will you wear your engine out?
.i just wondered what the pros and cons were of each system,and have i been told correctly so far?as for the paired injectors,this is to give a more accurate/quicker response than bank of four fired injectors,but its not worth going to individually fired injectors untill i have more accurate ignition control ie coil per plug,and even then its very little gain,and more to do with emmissions as has already been mentioned,apparently.hope im not teaching to suck eggs here,just passing on what ive been told(i havent a clue),as it seems of interest
-cheers,mike 
With the right injector positioning and flow rate you will make more power with sequential injection. It also has the ability to save around 10% in fuel consumption, as the engine will tolerate a leaner fuel mix without misfire or power loss. So even for a race car its worth doing.
Matt
Matt
Maybe Matt but not by much and if the injector timing isn't spot on then you will lose power and torque. To me it's an awful lot of trouble and dyno time to get the best package. If going sequential you may also need bigger injectors which could compromise the idle quality.
Now where's my holley carb, I seem to recall that made plenty of power Maybe of interest, a holley on an ls1 makes similar power to the efi set up.
Boosted.
Now where's my holley carb, I seem to recall that made plenty of power
Maybe of interest, a holley on an ls1 makes similar power to the efi set up. Boosted.
It all depends on how highly tuned the engine is, as taking things to extremes on the F1 engine I used to work on, a 'flat' injection timing map would cost around 70Bhp. So unless you're running a mechanical cam with lots of lift etc and tuned intake and exhaust lengths you're right the benefits will be marginal. But you should still get the benefits of being able to run leaner without power loss.
Matt
Matt
At full power, approaching 100 % duty ( appreciate you should run that high ), regardless of sequential or batch, the injectors are fully open anyway.
Size isnt that much of an issue.
I recently put together a Subaru engine running on 1000cc injectors with no idle issues. Low impedance type.
That should supply more than enough fuel for most engines.
Size isnt that much of an issue.
I recently put together a Subaru engine running on 1000cc injectors with no idle issues. Low impedance type.
That should supply more than enough fuel for most engines.
WHAT!? Ferk me, I thought I was doing well going from 180cc's to 220cc's....Well, we are looking for 600+ from it, so want to be sure we have ample fuel supply available.
Esp if we decide to throw some Nos at a later date ;-)
I have a set of 600cc injectors in my LS1 engine, although may look into an high-low imp converter and some larger ones at a later date should the need arise.
>> Edited by stevieturbo on Thursday 21st April 22:00
Esp if we decide to throw some Nos at a later date ;-)
I have a set of 600cc injectors in my LS1 engine, although may look into an high-low imp converter and some larger ones at a later date should the need arise.
>> Edited by stevieturbo on Thursday 21st April 22:00
When there is a plenum chamber involved on a naturally aspirated motor, the only correct answer is to use an airflow meter (AFM) where possible. I have never come across a plenum chamber setup (on the Rover V8) that would not work perfectly with an AFM, no matter how hot the cam. On the Rover motors, you will actually lose about 15lb/ft of midrange torque by eliminating the AFM.
Incidentally, you may notice that Griffany's monster Griff featured recently in Sprint magazine uses a 14CUX with Bosch AFM, and an Omex 150 for ignition management. There is no pressure drop across the AFM at full power, which indicates there is no restriction either. Further, the car has perfect manners, and is close to the power of throttle-body engines.
Whilst this was not a money-no-object job, I was given a free hand to use any system. The best value for money and best manners is represented by this solution.
Incidentally I have lifted the plenum off a 5.3 RV8 at full thrash on the dyno at V8D, and it lost 40 lb/ft immediately.
Logically, removing the airflow meter should help the power output, and that's what I thought too when I got started (about 14 years and 6,000 vehicles ago). However it makes very little difference to power except on very highly tuned motors, and actually damages mid-range torque to the tune of 10-15lb/ft.
The V8 does have plenty of surprises in terms of what you think it would like, and what it does like.
There is no better metering system than the hot wire or hot film airflow meter, as long as it is big enough (but not too big). This is because the engine's fuel requirements are really determined by the true mass of air that it is consuming at any given speed. Heated element meters score very heavily here since they compensate for temperature, barometric pressure, and humidity, all in one instrument.
If you use manifold pressure (MAP) sensing, then it is only provides a good estimate if you supplement it with air temperature sensor.
There is one drawback here however. As the engine ages the vacuum will drop off, which the management system seed as increased load and then pushes up the fuelling. This will increase the wear rate and fuel consumption. The heated element metering system again scores because it sees the reduction in demand and responds accordingly.
Throttle angle metering is the least accurate, but there is no choice where there is no plenum chamber. Again this needs air temperature and barometric pressure sensing to help it out. However it is never accurate since any given throttle opening and engine speed will cover a wide variety of loads. However the engine passes through them so quickly it won't be a major problem on a competition engine with throttle bodies!
From the point of view of the software in the ECU, throttle angle is the easiest to program. MAP sensing is quite a lot harder, and AFM is a whole order of magnitude more difficult. That's why I have only come across the Motec and Omex 700 (soon to be joined by the 600) that can do it. It all comes down to the compensations required on throttle motion - however when it is done properly you should not be able to tell any difference from the driver's seat.
I hope you found this helpful.
Incidentally, you may notice that Griffany's monster Griff featured recently in Sprint magazine uses a 14CUX with Bosch AFM, and an Omex 150 for ignition management. There is no pressure drop across the AFM at full power, which indicates there is no restriction either. Further, the car has perfect manners, and is close to the power of throttle-body engines.
Whilst this was not a money-no-object job, I was given a free hand to use any system. The best value for money and best manners is represented by this solution.
Incidentally I have lifted the plenum off a 5.3 RV8 at full thrash on the dyno at V8D, and it lost 40 lb/ft immediately.
Logically, removing the airflow meter should help the power output, and that's what I thought too when I got started (about 14 years and 6,000 vehicles ago). However it makes very little difference to power except on very highly tuned motors, and actually damages mid-range torque to the tune of 10-15lb/ft.
The V8 does have plenty of surprises in terms of what you think it would like, and what it does like.
There is no better metering system than the hot wire or hot film airflow meter, as long as it is big enough (but not too big). This is because the engine's fuel requirements are really determined by the true mass of air that it is consuming at any given speed. Heated element meters score very heavily here since they compensate for temperature, barometric pressure, and humidity, all in one instrument.
If you use manifold pressure (MAP) sensing, then it is only provides a good estimate if you supplement it with air temperature sensor.
There is one drawback here however. As the engine ages the vacuum will drop off, which the management system seed as increased load and then pushes up the fuelling. This will increase the wear rate and fuel consumption. The heated element metering system again scores because it sees the reduction in demand and responds accordingly.
Throttle angle metering is the least accurate, but there is no choice where there is no plenum chamber. Again this needs air temperature and barometric pressure sensing to help it out. However it is never accurate since any given throttle opening and engine speed will cover a wide variety of loads. However the engine passes through them so quickly it won't be a major problem on a competition engine with throttle bodies!
From the point of view of the software in the ECU, throttle angle is the easiest to program. MAP sensing is quite a lot harder, and AFM is a whole order of magnitude more difficult. That's why I have only come across the Motec and Omex 700 (soon to be joined by the 600) that can do it. It all comes down to the compensations required on throttle motion - however when it is done properly you should not be able to tell any difference from the driver's seat.
I hope you found this helpful.
Mark, if I may pick your brain... 
I have a guy 'insisting' that I should change the EFI setup on my 390SE for a hotwire.
However you know me, I have to fiddle and have acquired some bits to try my hand. The plan is to have the (spare) inlet manifold ported to match NCKs head porting job (dunno why they didn't do the manifold in the first place?) and shorten the trumpets by (IIRC Tim Lamont's recommendation) 15mm.
Next, the throttle body to be bored to 84mm, as I've seen done on SEACs, 450SE etc - but I don't know where the bigger throttle plate was sourced, is it a special?
I've acquired some 214cc injectors; I know they're not the same as the full-fat monsters but I would like to retain SOME economy!
Finally, the plenum insulator as used by Jeff Morgan.
Total cost (excluding machining and throttle plate) probably £100.
Am I wasting my time and if so where?
Would the hotwire be a miracle cure, given that it could then be re-mapped? I could do with a bit more midrange torque...
I have a guy 'insisting' that I should change the EFI setup on my 390SE for a hotwire.
However you know me, I have to fiddle
and have acquired some bits to try my hand. The plan is to have the (spare) inlet manifold ported to match NCKs head porting job (dunno why they didn't do the manifold in the first place?) and shorten the trumpets by (IIRC Tim Lamont's recommendation) 15mm. Next, the throttle body to be bored to 84mm, as I've seen done on SEACs, 450SE etc - but I don't know where the bigger throttle plate was sourced, is it a special?
I've acquired some 214cc injectors; I know they're not the same as the full-fat monsters but I would like to retain SOME economy!
Finally, the plenum insulator as used by Jeff Morgan.
Total cost (excluding machining and throttle plate) probably £100.
Am I wasting my time and if so where?
Would the hotwire be a miracle cure, given that it could then be re-mapped? I could do with a bit more midrange torque...
Mark Adams said:
However it is never accurate since any given throttle opening and engine speed will cover a wide variety of loads.
i can't get this bit straight in my head Mark .. can you shed some light maybe?
If you have a fixed throttle and rev number, there must be a load on the engine to do it .. now you can't vary the load without either the revs going up or down, or modulating the throttle to keep the revs the same as load avries .. so how does one throtle and rev position cover a variety of loads?
For any given throttle and rev position there will be a fixed airflow unless you change the air density .. this is how throttle/rev systems work as you know .. it's not important to *know* what the airflow is in reality, just that you can fuel it accordingly.
.. it doesn't matter which way i look at that, I can't make it work in my head.. nad i'd really like to understand how that would work.
wedg1e said:
Mark, if I may pick your brain...
I have a guy 'insisting' that I should change the EFI setup on my 390SE for a hotwire.
However you know me, I have to fiddle
Next, the throttle body to be bored to 84mm, as I've seen done on SEACs, 450SE etc - but I don't know where the bigger throttle plate was sourced, is it a special?
I've acquired some 214cc injectors; I know they're not the same as the full-fat monsters but I would like to retain SOME economy!
Finally, the plenum insulator as used by Jeff Morgan.
Total cost (excluding machining and throttle plate) probably £100.
Am I wasting my time and if so where?
Would the hotwire be a miracle cure, given that it could then be re-mapped? I could do with a bit more midrange torque...
I would say do it anyway and try it
.. experimenting is 99% of the fun of doing work .. if you're not finding stuff out there's little little interest IMO .. just do it MRMike - absolutely correct. It's probably not so important on a competition car, which will be re-fettled or modified regularly. However I would consider it essential for a road-going motor.
Out of interest, when Rover used to use MAP, there was a re-adjustment to the fuel trim at specified mileages (although I can't remember what that was).
Jools - I know what you mean! It's definitely one for the Crypton Factor...
The difference is quite subtle really, and it is small enough not to be an issue for most people. It probably only matters to detail-obsessed anoraks like me in fact.
When Throttle Angle motors are mapped, it has to be steady state so no problem there. The load issue is rarely significant for rising throttle, but does come into play momentarily on a trailing throttle as you "drop-on" to a site or decelerate through it.
It's an effect you can see especially on automatics, and most of my off-road customers are automatics. Also it makes idle stability really difficult on an automatic when you put it into gear and thereby add a huge load. This is another reason why you need a lot of load sites around idle.
Out of interest, when Rover used to use MAP, there was a re-adjustment to the fuel trim at specified mileages (although I can't remember what that was).
Jools - I know what you mean! It's definitely one for the Crypton Factor...
The difference is quite subtle really, and it is small enough not to be an issue for most people. It probably only matters to detail-obsessed anoraks like me in fact.
When Throttle Angle motors are mapped, it has to be steady state so no problem there. The load issue is rarely significant for rising throttle, but does come into play momentarily on a trailing throttle as you "drop-on" to a site or decelerate through it.
It's an effect you can see especially on automatics, and most of my off-road customers are automatics. Also it makes idle stability really difficult on an automatic when you put it into gear and thereby add a huge load. This is another reason why you need a lot of load sites around idle.
Mark Adams said:
On the Rover motors, you will actually lose about 15lb/ft of midrange torque by eliminating the AFM.
Is there a gain in bhp to compensate? Often i read or hear that mods gain in one field but loose out in the other.Id not be too disappointed to loose torque if i would gain bhp instead.The rv8 seems to easily make torque,but bhp seems the more difficult to aquire?Also,thinking about it,are you refering to any amm?I'd have thought that my std one was restrictive enough, that removing it would only mean a gain in airflow,and possibly therefore,more torque and bhp?
>> Edited by mongoose on Saturday 14th May 10:37
mongoose said:Anyone???
On the Rover motors, you will actually lose about 15lb/ft of midrange torque by eliminating the AFM.
Is there a gain in bhp to compensate? Often i read or hear that mods gain in one field but loose out in the other.Id not be too disappointed to loose torque if i would gain bhp instead.The rv8 seems to easily make torque,but bhp seems the more difficult to aquire?Also,thinking about it,are you refering to any amm?I'd have thought that my std one was restrictive enough, that removing it would only mean a gain in airflow,and possibly therefore,more torque and bhp?
>> Edited by mongoose on Saturday 14th May 10:37
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