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Home > A-Series EFI / Injection > Throttle Body Options

Barrieri

307 Posts
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Sorry for waking up an old discussion.

Around three years ago I got to fuel inject a 998cc, mildly turboed, but otherwise stock engine. The engine was port-injected using the MS3x, an MPI (plastic) throttle body and MPI manifold.

I've always been a bit disappointed with the tip-in that the engine exhibits, and I've played around endlessly with acceleration enrichments. At the moment I have a bit of time on my hands and was going to try and fit a smaller (say 40 mm) throttle body instead of the larger MPI one.

I know AT power does a 40 mm throttle body, which is a nice bit of kit, but the price tag is a bit on the high side. Are you guys aware of any OEM 40 mm throttle bodies?

Thanks,
Carl


Rod S

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I can't answer your actual question (ie, where to source a smaller throttle body) but just a general observation...

If you are really doing port injection, why should the throttle body size matter ?

It should be far enough before the injectors to have minimal effect on airflow at the actual ports, I would have thought.

Turbo or N/A ?

On mine the throttle body is about 600mm from the ports/injectors and the air goes through a plenum where I have a flow divider to straighten everything out. So the throttle body size is irrelevant in my case.

As you are using injection, is it set for alpha-n or speed/density ?

If the latter (which would be the most logical for an "A" series), where is the MAP sensor plumbed in ?

Schrödinger's cat - so which one am I ???


Barrieri

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Hi Rod,

Thanks for your reply. I believe I have read on an old post here on the forum that the tip-in issue is caused by an oversized throttle body. Since my engine is a 998cc and the MPI manifold & TB that I'm using are from a 1275cc engine I thought it made sense. I believe the MPI TB that I'm using is about 50 mm diameter (which compared to the 38mm SU carb) is really large.

In reality the tip-in issue that it shows can be lived with, in fact I've used it like this for a long while now. It is only a bit annoying when I'm stuck in traffic going up a sloped road, otherwise doesn't bother me at all.

To answer your questions, yes it is turboed (only 7psi). I'm using MAP as the fuel/spark load parameter, and TPS only for acceleration enrichments. The MAP is being read at the small volume between the runners and TB of the MPI manifold, but the 3 mm silicon pipe is relatively long and goes all the way to the dashboard where the ms3x (and inboard MAP sensor) is located.

By the way at the moment I'm using the 875cc/min Siemens Deka injectors (one in each runner) with the one long pulse method. Tip-in was also an issue when I used the standard MPI injectors on the N/A engine.


Rod S

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Do you have a wideband connected to your MS3 so that you can see what actually happens when you get the "tip in" issue.

Personally I wouldn't use an MS3 on siamese ports even though Paul has shown it to work in his case.

The "long pulse" is available in the MS2 siamese code and I use it above 3k RPM but I would never use it at low RPMs, especially with large injectors (and 875cc is very large for a 998, my primaries are only 1000cc for a 1360).

If you have some data logs from your MS3 (hopefully including a wideband AFR reading during the transient), attach them to your next post.

Schrödinger's cat - so which one am I ???


Barrieri

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Member #: 11231
Senior Member

I don't have any logs in hand at the moment. Most of the time I do the tuning round the block whilst my brother drives. Checking the AFRs during tip-in is not a bad idea, but I can't do that right now.

At the moment I'm waiting for my 14point7 widebands to arrive. I've just removed the Innovate widebands as they have consumed more sensors than they should have with the E8 error.

Why should the single long pulse be a problem at low rpm though ?


Rod S

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On 10th Sep, 2020 Barrieri said:

Why should the single long pulse be a problem at low rpm though ?


In theory it shouldn't and Paul seems happy with it but when I setup my MS2 - where it just an add-on option - I tried it, just out of interest, but couldn't get it right at low RPMs so have it set to cut in only above 3k RPM (its advantage over the two short pulses is only that you can get more fuel in if needed which is only needed at higher RPM/load).

Which, if you look up what Rover did with the MPI setup, using a 4 channel MEMS, they drive the injectors with two short timed pulses at low RPM then switch to the long pulse only at high RPM or load.

Now they probably only did that to meet the emissions standards required at the time (the SPI would not have met them, hence they "upgraded") but I find it's a lot easier to get the low load/RPM AFRs balanced between the inner and outer cylinders with two short timed pulses of different lengths and because I have that option, that's what I do.

Re. the Innovates, your hardly the first person to find they kill sensors..... It is so well documented on the web I'm surprised people are still buying the stuff. Trust me, you'll be a lot happier with the 14point7 stuff, but if you're buying from Alan direct (the bits I use aren't available from any second party retailers, only Alan direct) then you are probably going to have to be patient.....

Schrödinger's cat - so which one am I ???


Barrieri

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On 11th Sep, 2020 Rod S said:

Re. the Innovates, your hardly the first person to find they kill sensors..... It is so well documented on the web I'm surprised people are still buying the stuff. Trust me, you'll be a lot happier with the 14point7 stuff, but if you're buying from Alan direct (the bits I use aren't available from any second party retailers, only Alan direct) then you are probably going to have to be patient.....


Yep, actually I bought them way back in 2016. I tried the 14point7 stuff around a year ago on my K1100 and I liked it, even though to be honest I haven't used it for long hours. I actually bought the stuff from Alan.


On 11th Sep, 2020 Rod S said:

I find it's a lot easier to get the low load/RPM AFRs balanced between the inner and outer cylinders with two short timed pulses of different lengths


Why is it that the two pulses are of different lengths? I was under the impression that each of the two individual pulses go to feed the two successive cylinders, i.e. one pulse goes to the inner cylinder 2 and the other pulse goes to outer cylinder 1. Hence, should be the same length. Is this because the inner cylinder has one whole revolution (or actually 270 DegCA) available for injection, and the outer cylinder has only 180 DegCA?

Edited by Barrieri on 11th Sep, 2020.


Rod S

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On 11th Sep, 2020 Barrieri said:

Why is it that the two pulses are of different lengths? I was under the impression that each of the two individual pulses go to feed the two successive cylinders, i.e. one pulse goes to the inner cylinder 2 and the other pulse goes to outer cylinder 1. Hence, should be the same length. Is this because the inner cylinder has one whole revolution (or actually 270 DegCA) available for injection, and the outer cylinder has only 180 DegCA?

It's the basic charge robbing issue with any siamese'd inlet ports.
But especially so on "A" and "B" series engines.
When port injecting it's nothing really to do with the fuel (because I can choose that) but the mass air is different because when the inlet valves open in sequence (and overlap each other), the way the air accelerates down the joint runner (whether sucked or blown there) the inner cylinder get less and the outer cylinder more.

The so called "scatter" cams are one way to try to get over it on carb'd engines but with a symmetrical cam and a fuel injection system that allows different pulse width per cylinder I just inject a bit more into the outers.

What you will be doing, maybe without realising it, is that more of your single pulse goes into the outer when you have got the balance right.

With my 1000cc injectors I use an injector base dead time of 0.8mS (I use a make of low-z injectors that are very fast opening) and still see pulse widths of only around 1.2 to 1.3 at idle, so that is why I find it so sensitive.
I just use the VE tables - with the MS siamese code I get three, one for the outers, one for the inners, and one for the long pulse (if it's enabled) - and I just offset the inner and outer VE tables by about 10% and the third one is a strange combination of the first and second because the dead time is only coming into play once. And there are obviously three injection timing tables to make it all work.

End result is this, if you haven't seen it before (just at idle),

https://www.youtube.com/watch?v=WgKJX13B1xE

I know there are a lot of other benefits of using an MS3 but, although it can get close, it cannot replicate all the features of the MS2 siamese specific code so, having been involved with Jean from pretty early on, I stick with what I know.

And for all the additional I/Os of an MS3 that I don't get with an MS2, I just use one of Jean's IOx boards.

Schrödinger's cat - so which one am I ???


Rod S

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Just to add, if you're looking for where the discussion about siamese fuel injection started, it's here,

http://www.starchak.ca/efi/siamese.htm

Or at least I think it was here - I didn't get involved until a lot later....

Schrödinger's cat - so which one am I ???


Paul S

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Podland

I used a throttle body off a Ford with a progressive linkage (pictured in first post of thread). It does not eliminate the tip in completely but I adapted my driving style to suit.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."


jbelanger

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Montreal, Canada

Another reason for the fueling difference between the inner and outer cylinders is that the fuel from any wall wetting will go mostly to the inner cylinders due to the 540/180 degree split. That will also mean a shorter pulse width for the inner cylinders.

http://www.jbperf.com/


Graham T

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I think, but I cannot be 100% my TB on my original 998% was off of a 98 Hyundia of some sort. I have it somewhere, but off the top of my head I cannot remember the size or what model it was off of.
But I do have photo’s of it, if they are of any help





I had to make a thin adaptor plate to fit it directly to the MPI inlet manifold. Also I was able to use the oem pipe work to connect the IACV.


Edit -

On 14th Nov, 2009 Graham T said:

I am using a Hyundi Accent TB for the first trial. It has a 46mm Throat and the TPS already on it.


I knew I had put it in some text somewhere…

From this thread: http://www.turbominis.co.uk/forums/index.php?p=vt&tid=319227

- end edit




With regard to the injectors, I could never get a very good idle with the 875cc injectors on the 998, but then that might be because with the ms2 Siamese code the pulse width had to be so low that it was not reliably and consistently opening the injectors. The 630cc injectors (same and Paul used I think) were ok, but still not great.


Ultimately Rods low Z setup is far superior on tick over to the high Z injectors. It was much smoother and I was able to get very good AFR’s (low 14’s) consistently on tick over. My setup now on the 1310cc engine with the 875cc/min Siemens Deka injectors I can manage around 13 – 13.5 AFR on tick over. Try to make it any leaner and the engine is hunting and stuttering.
I never got to try the low Z on hard driving because I blew out the o’rings in the injectors on the first serious high boost run. The first I knew of it was the smoke coming from under the hood and the strong smell of petrol when I slowed. Hence I took the injectors out and never did any more testing with Rod’s ECU.


Which 875cc/min Siemens Deka injectors Are you using? The longer ones or the shorter ones?

The longer ones I have found to work much better. They have a tighter spray pattern (10-15Deg IIRC) than either the shorter 875cc/min or even the 630cc/min, both of which I think have a 26deg spray cone.
The “pencil stream” seems to suit the A series, and getting AFR balanced is a lot easier than with the wider cone pattern.
I’m not sure if it is because of potentially less wall wetting or maybe something to do with the atomisation of the fuel…



Wideband controllers:




On 11th Sep, 2020 Barrieri said:
On 11th Sep, 2020 Rod S said:

Re. the Innovates, your hardly the first person to find they kill sensors..... It is so well documented on the web I'm surprised people are still buying the stuff. Trust me, you'll be a lot happier with the 14point7 stuff, but if you're buying from Alan direct (the bits I use aren't available from any second party retailers, only Alan direct) then you are probably going to have to be patient.....


Yep, actually I bought them way back in 2016. I tried the 14point7 stuff around a year ago on my K1100 and I liked it, even though to be honest I haven't used it for long hours. I actually bought the stuff from Alan.




With either the Innovate LC-1 or LC-2’s it was eating LSU’s – I mean every couple of months I had to replace 1 or all 3, which was an expensive hobby.
As soon as I swapped to 14point7 controllers I have had one LSU failure in I think 4 years.

Edited by Graham T on 12th Sep, 2020.

’77 Clubman build thread
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=618189

Siamese 5 port EFI testing
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=611675


Barrieri

307 Posts
Member #: 11231
Senior Member

Thanks all for the comprehensive explanation about the different pulsewidth lengths.

Attached is a list of the options I found so far which offers 38 - 40mm throttle body. I don't think I'll be going for any of these at the moment though. I'm tempted to try one from Aliexpress, but the last order I made took almost 3 months to arrive to Malta due to CV-19. So for now I'll be on the lookout, at least until the 14point7 widebands arrive.

https://www.ecotrons.com/components/tb/ecot..._throttle_body/

https://www.aliexpress.com/item/32811884426...earchweb201603_

https://www.aliexpress.com/item/40011845640...earchweb201603_


Rod S

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On 12th Sep, 2020 Graham T said:
Ultimately Rods low Z setup is far superior on tick over to the high Z injectors. It was much smoother and I was able to get very good AFR’s (low 14’s) consistently on tick over. My setup now on the 1310cc engine with the 875cc/min Siemens Deka injectors I can manage around 13 – 13.5 AFR on tick over. Try to make it any leaner and the engine is hunting and stuttering.
I never got to try the low Z on hard driving because I blew out the o’rings in the injectors on the first serious high boost run. The first I knew of it was the smoke coming from under the hood and the strong smell of petrol when I slowed. Hence I took the injectors out and never did any more testing with Rod’s ECU.

My fault entirely...
IIRC it was a day at Robert's when I brought them (and my spare ECU) over and I forgot to tell you to swap the inlet "O" rings for Bosch ones.
The ones I use are for high performance Honda and Subaru engines and they have a different shaped inlet fitting on the fuel rail. So the supplied "O" ring is the wrong size for a normal setup.
Many emails later we did find out these particular injectors are also available in a version with standard Bosch rail fittings but by then it was too late...
A shame because it would have been nice to get the data on Graham's engine for a straight high-z vs. low-z comparison.

Schrödinger's cat - so which one am I ???


Graham T

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On 13th Sep, 2020 Rod S said:
On 12th Sep, 2020 Graham T said:
Ultimately Rods low Z setup is far superior on tick over to the high Z injectors. It was much smoother and I was able to get very good AFR’s (low 14’s) consistently on tick over. My setup now on the 1310cc engine with the 875cc/min Siemens Deka injectors I can manage around 13 – 13.5 AFR on tick over. Try to make it any leaner and the engine is hunting and stuttering.
I never got to try the low Z on hard driving because I blew out the o’rings in the injectors on the first serious high boost run. The first I knew of it was the smoke coming from under the hood and the strong smell of petrol when I slowed. Hence I took the injectors out and never did any more testing with Rod’s ECU.

My fault entirely...
IIRC it was a day at Robert's when I brought them (and my spare ECU) over and I forgot to tell you to swap the inlet "O" rings for Bosch ones.
The ones I use are for high performance Honda and Subaru engines and they have a different shaped inlet fitting on the fuel rail. So the supplied "O" ring is the wrong size for a normal setup.
Many emails later we did find out these particular injectors are also available in a version with standard Bosch rail fittings but by then it was too late...
A shame because it would have been nice to get the data on Graham's engine for a straight high-z vs. low-z comparison.





Well, I might have to revisit this again.
This conversation reminded me that I never got a reply from RC fuel injection about flow rates for those PL4-1000, So I have just emailed them again.

The coupe only just passed MOT on emissions this year and I’m already at 19% duty cycle for 193BHP.
I had considered a rise rate (1.3-1 or 1.5-1) pressure regulator, but as I will need a second MS2 and more injectors, this might just be the way to go. But that said, I need to check that I left enough room in the injector bosses for the fat body injectors.

’77 Clubman build thread
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=618189

Siamese 5 port EFI testing
http://www.turbominis.co.uk/forums/index.php?p=vt&tid=611675


stevieturbo

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Northern Ireland

IMO, if you need some high flow injectors, put something modern in it like an ID1000, high Z.
Or if larger ID1300X or whatever it's called.

They are just superior to that old LowZ stuff like RC offer.

Just make sure filtration is good, a lot of the modern stuff need sub 10 micron.

Edited by stevieturbo on 15th Sep, 2020.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will


Barrieri

307 Posts
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Senior Member

I was looking at a set of K1200RS throttle bodies (that belong to my brother) the other day and noticed that it's bore is actually around 38 mm. I only measured with a ruler and a thread, so don't quote me. I'll double check the measurement. It also seems that I can dismantle the assembly and use just the barrel at the TPS end and still have an independent single throttle body.

It seems that the throttle bodies assembly of the k1200rs cost twice as much as that for the k1100lt. Are you guys aware of any differences in the two ? Particularly with regards to bore size ?



Rod S

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Apologies to Carl (Barrieri) for highjacking his part of this thread , but,

On 15th Sep, 2020 stevieturbo said:
IMO, if you need some high flow injectors, put something modern in it like an ID1000, high Z.
Or if larger ID1300X or whatever it's called.

They are just superior to that old LowZ stuff like RC offer.

Just make sure filtration is good, a lot of the modern stuff need sub 10 micron.


Are you serious Stevie ???

Have you actually looked at the datasheets of the "Injector Dynamics" ones ???

They specifically say "All Injector Dynamics Products are Designed Solely for Off-Road Motorsport Use - © 2013 Injector Dynamics"

And, if you'd looked, you would see why if you'd have looked at the slope/offset table the offset at the normal road car 3.5 bar pressure is appalling - they are designed for race cars running very high pressures and, even then, if you look at the table, they are even worse at high pressures.

As far as I know, Graham is still running Seimens/Decker high-z injectors (large ones) so are you saying they are not a good make of high-z ones ???

The only comparison we really wanted to my low-z RC ones was at idle - where the dead time (open/close) becomes really important running the MS2 siamese code - because the pulse widths are tiny.

From the limited data (before the "O" ring issue) that Graham emailed me, I would concur with his view that the RC low-z ones were better then the Seimens high-z ones.

The key with low-z is to get the driver circuits right to optimise their faster open/close ability. Put them on a standard ECU and you will probably fail. And that's why Graham borrowed my spare ECU so we could be sure the driver circuits were right for the RC ones.


Schrödinger's cat - so which one am I ???

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