View Full Version : Is Microtech MTx8 true sequential?
A friend was telling me that the Microtech MTX8 is already in sequential injection mode out of the box. I wonder if this is the true sequential injection and if so, wouldn't it need larger injectors to give similar hp as in other injection mode such as batch or multipoint?
10sec rx7
30-10-02, 07:36 AM
sequential injection would not require larger injectors, sequential injection means that the injectors fire and the right time when the valve or port is opening, batch or group just fires all 4 the same time and can be a bit rough at idle and emissions are not as good. true multipoint will run sequential injection.
the microtech is true sequential injection, it can be swapped in to group mode at any time.
As the rpm gets higher, the valve opening time gets much shorter and in sequential injection mode, you need to inject more fuel/ms during the opening time to ensure there is enough fuel going thru the port during the short opening time and into the chamber. That's why you need bigger injectors than others do as you run out of fuel capacity earlier. As for batch or multipoint mode, the fuel is stored up behind the valves ready to be despatched when the valves open .
10sec rx7
30-10-02, 12:56 PM
as the rpm goes up so does the injector pulses, the injecotors dont just pulse at the same speed al the way through the rev range
who said you need bigger injectors when you run sequential mode??
Most modern multipoint cars run sequential injection, multipoint isnt a injector firing mode, it is where you have 1 injector per inlet runner firing at the valve, you will find most efi cars have this.
its all about fuel atomisiation, if the fuel is pooling on the valves this isnt good, you want a good mix of air and fuel going in there,
Not only pulse speed goes up so does the pulse width.
Sequential needs bigger pw/cycle than other mode at the same injector size at high rpm . So you hit 100%DC earlier.
denmaster
30-10-02, 04:51 PM
Yes, the MTX8 is capable of true sequential injection provided that the CAS can tell it where TDC is. If it cannot, then it will run in group/batch injection with a minor change in the configuration.
My experience has been that there was no need to increase injector pulse widths to maintain the same AFR's when swapping from group/batch fire to sequential firing.
You will find that sequential firing engines are also generally more fuel economical, at least as far as stock engine management systems go. This is evident in the Mitsubishi engines where early on they were batch fire, but as the transition has been made towards GDI and lean burn engines we see implementation of sequential injection.
When I think about it, there's probably a whole lot of other little things to consider as well (such as what 10sec_rx7 brought up with atomisation and pooling) which are in turn related to how the engine has been ported, size of throttle body, intercooler pipe diameter, injector location, spray pattern etc. At the end of the day, who knows...
To be fair to the Microtech product, saying that its default configuration of a more modern method of firing injectors sequentially that is easily swappable to group/batch fire anyway is some cause for thinking it is an inferior product is a poor justification. If you mention processor speed, resolution of the values, non linear behaviour of the sensors etc. perhaps you may have an argument... Even then, :rolleyes:
Can people please realise that its the singer not the song... ;)
LG
With the Microtech is it possible to map the end of injection timing, eg alter the point at which the injector opens and closes in relation to the valve timing or is it simply set at one spot?
No the Microtech injection event end point is fixed.
I think only Motech and Autronic provide that facility (please correct me if I am wrong) and it is only good for wringing out the absolute last few HP and for slightly tidier emissions.
One point with ref to injector sizing. If an ECU is running banked injector firing and is firing those injectors once every rev (ie twice for each cylinder's 4 stroke cycle) THEN and only THEN will the injectors be effectively double sized.
But you will notice that when people are talking about being at or near max duty cycle, it really means that they are using up nearly all the milliseconds available at high revs for opening the injector just once per two engine revolutions. So if your injectors are marginal they are marginal regardless of firing mode, and can in fact be more so if in double fire banked mode because of the wasted time with the pintle opening or closing is doubled.
cheers
Even in batch, there should be something to tell the ecu when No.1 or whichever cyl TDC is coming up. I am sure Microtech needs it.
If you still find that you do not need to fatten the pulse width switching from batch to sequential, I have a feeling that it is not true sequential.
I don't doubt sequential injection give fuel economy but my concern here is not about fuel economy when you are trying to build a drag race car, but rather the concern of having to buy larger and expensive fuel injectors just to get to the same power performance as on other injection mode which requires less injector capacity.
On the issue of fuel pooling behind the valves, I tend to think that while being retained behind the valve, the fuel actually has more time mixing up with the intake air coupled with the fact that the heat on the valve and the port actually helps in "atomising" the fuel thereby producing a better mixture before it gets into the combustion chamber.
As you mentioned, the spray pattern of the fuel injector plays a larger part in the atomisation of the fuel. However, GDI is not the same as the normal sequential injection as GDI involves direct injection in the combustion chamber.
To clarify, I have never had any intention to say anything bad about Microtech. What matters to me is whether it suits my particular need and application. Of course, since you said it can be easily configured to work in other mode, it is still a friendly piece of equipment as other programmable ecus out in the market. Perhaps Microtech use it(sequential injection) as the main selling point for their ecus just to tell others you can have sequential injection for a much cheaper price.
denmaster
31-10-02, 06:17 PM
If you consider the situation where you're running batched fuel ignition, with a single coil and a distributor, you'll see where an ECU doesn't need a TDC signal :)
What do you mean by not running in true sequential ? I'd be keen on doing some reasonable research to figure out whether any ECU I use is playing games with me (i.e. when its not actually firing the fuel sequentially but should be...) I've hooked up the injector output to a CRO and it looked good, what method would you use for checking that the ECU really does what it says it does ?
If we're talking about drag racing, even carburettors can do a great job ! Fuel injection is about drivability and refinement without sacrificing power. Didn't hot4's or fastfours do some experiment where they poured in methanol into the carby directly ? Seems really crude, but hey, it made more power :D
LG
I know the MoTeC does give you the opportunity to map the end of injection timing, I was just curious about the new Microtech units.
10sec rx7
01-11-02, 10:37 PM
squential will only work if there are referance points for all cylinders, a single referance point will only ever work in batch mode no matter what ecu you have,
you cannot adjust the pluse timing on the microtech,
you will not need larger injectors on a sequential setup, it should be a moreefficant way of firing the injectors, i cant see it needing larger injectors at all, at the end of the day you are firing for example 4ms of fuel in each cycle into each cylinder 4ms is 4ms weather they all fire at once or one at a time.
the microtech is full sequential with the correct crank angle sensor.
A programmable ecu capable of sequential injection should also be fundamentally capable of allowing the user to trim every individual fuel injector injection time for purpose of making sure all cylinders are getting the right amount of fuel they actually need in view of the imperfect design of intake manifold, different compression level between the cylinders, potential differences in flow rate between injectors even they are of the same make and capacity, etc.
In additon, the ecu should also be able to allow the user to specify the actual timing or angle at which the valve is closed/opened.
Whether it is sequential or batch or multipoint, the ecu still needs a timing reference or signal to fire the injectors/ignition whether it is from the distributor, crank angle sensor, optical sensor, or other method of triggering.
wira. You aren't listening.
There is a difference between individual cylinder trim (where the duration is adjusted for each cylinder, which is very hard to set up correctly unless you have exhaust pyrometers installed in every leg of the exhaust manifold) and injection enf dpoint time adjustment which is where the point at which the injector is closed is set in degrees ABDC (or whatever angle measurement you like).
Some aftermarket ECUs have both of these. Almost nobody uses EITHER of them as they are only for chasing the very last horsepower out of the stable and are not worth it for the average Joe Blow.
cheers
the end of injection timming needs to change as the rpm gets higher so that the fuel can delivered at the right time
I have found quiet good power gains from moving this point
we got about 40 extra foot pounds of torque on a 13B t on the engine dyno by moving it around at different rpm points
only the " high end " systems have this feature
John P
Hi Merlin,
I suppose you were running batch injection mode on the 13B?
no sequential injection
why u ask??
and steve ur are wrong about the ref point for each cyclinder
the ecu needs two things to do sequential fuel and igintion ( ie one coil per plug)
1 is a refernce signal that tells the ECU that the engine is spinning over
u need to enter the no of pulses the ECU gets in one crank rev
so that ur rpm count is correct
2 is a sync signal that tells the ECU where no 1 cylinder TDC is
from this the ECU can calculate when to fire each injector and coil
John P
Hi Merlin,
Were you saying "No sequential injection" or "No, sequential fuel injection" ?
Would the injection phasing you described work on other injection mode such as batch or multipoint?
Does the angle of injection BTDC increase with higher rpm in your case?
"No, sequential fuel injection
sorry forgot the comma
batch is when all injectors are fired at the same time
ie all are fired when each valve opens
multi point
describes where the injectors are placed
ie one injector near the valve
rather than all together at the throttle body
and yes the from memory we started with about 180 deg at 1500 rpm and finnished with 270 odd at 8000
John P
Merlin,
The reason I asked you about the injection phasing is that my buddy is facing problem of slow build up of rpm from 7000rpm to 8000 at WOT. He is running about 24 deg timing Advance on 97 RON and still having this problem. By the way, he is trying to tune up a Nissan CA18det with 264/272 cams. Any clue?
I would say its more a mechanical problem
ie the cams are not set corectly
and i would need to talk to him to help with that
or its a intake or exhaust problem
u have asked a real hard one to answer on here
i could type 10 pages and still not cover it
if u like u can get him to ring me ??
pm me and i will give u my number
John P
He is running 3" throttle body, custom intake manifold, ported head, 4" exhaust system, T04R turbo on custom exh manifold, 720cc injectors, huge Trust front mount intercooler, and Haltech E6K ecu.
sorry if this sounds rude
but
i need more info to help
call me 0418 324 700
John P
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