L-Jet on Euro Motor

[kmead]

I think this would be better placed in a new thread.

One question is with a more efficient air pump, which is what the engine is, has the AFM maxed out in terms of angle of flap displacement at full throttle? If yes then at what RPM is that occurring? I doubt that is happening at 4000 rpm. With your approach does the increase in pressure rise progressively? If not then you would effectively be dumping a lot of fuel (relatively) which would not be well metered.

I honestly suspect the existing FI would compensate appropriately to over 100hp. The 124 Spider set up is nearly identical and is good for 120 at least with no modifications to the system. I don’t know the exact differences between the two but the injectors I believe are the same, the computer has a different PN and the AFM is a different pattern due to being mounted to the air filter housing. I don’t know if the actual specs of the AFM is different or identical to the X one (throat dimensions etc). One could argue if the 124 system is enough different then the possibility exists to switch the parts from a 124 to the X so you have a fully controlled system.

I suspect you are overthinking this.

I never over think anything…

 

[Stuartc]

I completely agree and probably over thinking it but that’s what I do.

So to answer a couple of your questions I’ll quote from my Bosch FI book;

“On engines equipped with L-Jetronic as original equipment, the air-flow sensor is most affective at low to moderate engine speeds. Above 3500 to 4000rpm, the sensor flap has reached the end of its travel. It is fully open at about the point where maximum volumetric efficiency is reached. Above this rpm point, air flow into the engine per stroke actually goes down, so you don’t want any more fuel for the mixture. In this higher rpm range, fuel delivery becomes a function of engine rpm rather than air flow”.

The “device” I’m proposing only increased fuel rail pressure at near to or WOT and is adjustable for pressure and when it starts acting based on manifold pressure - so it claims
Good suggestion with the 124 sport/spider/131 as they all use identical L-Jet may look into that.
Has anyone tried this?

I forgot to mention that first thing would be to measure the AFR to obtain if the system was already adjusting to the higher output before adding anything further so you are correct.

 

[Dr.Jeff]

Maybe this should be a new thread as Karl suggests.

"I’ll quote from my Bosch FI book" I think if you study what Bosch is saying in detail, the AFM is the limiting factor in terms of engine efficiency. And by their own words the stock AFM (on the X) will not support much increase in performance. At that point adding more fuel only makes the AFR richer, which is not desirable. In other words the AFM is a big obstacle to increasing the performance on these engines. That is where using a aftermarket ECU comes in, allowing the elimination of the AFM (in addition to being programmable).

If the 124 ECU is designed/programed with a mixture for more airflow than the X's (my understanding is it is), and the AFM is able to support it (which it should), then using the 124 AFM and ECU may help in your goals. But you cannot start mixing and matching stock Bosch FI components, it doesn't work that way. For example I've seen guys try a larger AFM from a BMW on a smaller engine and it failed. Same with using one ECU on another system. The components are engineered and programmed to function together. So you pretty much need to use a complete 124 system, meaning the AFM, ECU, injectors, FPR, sensors, etc. However none of these Bosch ECUs are programmable, and the two engines they were engineered for are different, so it still won't be right. For example the intake manifolds have different air flow characteristics, the heads are of differning efficiency, etc. A better approach would be a aftermarket FPR.

Karl brings up a good point, the stock FI on the X might support 100HP. However I'm not sure, some testing and measurement would be required. But "HP" isn't the defining factor, engine efficiency and other parameters are. To be honest I doubt it will really work properly as far as maintaining correct AFR's across the range. You definitely need a wide band O2 to check what's going on.

Based on my experiences with attempting to modify the stock Bosch Jetronic systems, I don't believe the idea of adding a different FPR will work. They don't respond to anything more than vacuum and there is more to maintaining a proper AFR than that. However I can say the stock X fuel pump will not adequately support the fuel requirements if you need much more pressure. Although the pump can create the higher pressure, it loses volume in the process. Pressure and volume are inversely related; to get more pressure you have to restrict flow (that's how a FPR works). And volume (flow) is what the engine needs, not pressure. This is a common mistake. The amount of time the injector is open and the size of the injector is how the fuel volume are best managed. That's where a standalone ECU comes in. But there are larger Bosch fuel pumps that will supply the needed volume and pressure. And they are a direct swap for the stock one. Again, the entire system needs to be matched and balanced to work.

Also don't forget the ignition and other supporting systems. Really the best approach would be a aftermarket ECU and all the things that go with it.

Obviously just increasing the fuel won't make more power. You mentioned cam, compression and headwork. What specifically are you doing to the engine?

 

[Stuartc]

I was hoping that an earlier respondent would reply again with a bit more feedback on how the car performed after putting the l-Jet on a carby head.

As I’m doing a full restoration of the car whilst the engine is out I was planning on a full rebuild. Even though engine is low mileage and runs fine it’s been untouched from day one (why it’s was good buy) and needs a good clean up. Whilst engine is out plan is to optimise head, nothing radical just optimisation and running std euro cam. I’ve had an 81 previously and was more than happy with its performance only difference being it had twin DCNF’s. The std euro cam is very good.

My plan is to make the most of the Factory L-Jetronic and once I’ve got car back on the road change out the L-Jetronic for Microsquirt. I’ve just sourced a MkI Uno Turbo crank position sensor, cradle & pulley and apart from the pulley should directly fit onto the M202.15 block ready for the Microsquirt system. As I have A/C the pulley will need to be customised somehow so the pickup can sense TDC. But I’m not planning the Microsquirt changeover for a while mainly as I’d like to enjoy the car for a while and get used to it before starting to improve the injection side of things and all the extra work that involves.

If the L-Jetronic functions fine on std euro engine with what I’m planning with head wise optimisation and get close to 100bhp I’d be happy. Whilst I’d be overjoyed if it behaved as well as my ‘81 with twin DCNF’s I’d be surprised but happy to trade of some raw power for ease of use especially as my ‘88 X1/9 is air conditioned.

 

[Jefco]

I got a Bayless performance head (upgraded to the 231 deg. cam, equal to 35/75 Daytona), Vick Auto pop-up pistons with small reliefs, their upgraded injectors, and Allison's header/exhaust (with cat) on my '86; the stock L-jet FI has no problem keeping up. I think it's got something around 100HP, possibly a little more.

 

[Stuartc]

I got a Bayless performance head (upgraded to the 231 deg. cam, equal to 35/75 Daytona), Vick Auto pop-up pistons with small reliefs, their upgraded injectors, and Allison's header/exhaust (with cat) on my '86; the stock L-jet FI has no problem keeping up. I think it's got something around 100HP, possibly a little more.

Do you have any details regarding the “upgraded” injectors? Ie part number? Should be marked on the injector.
Thanks

 

[Dr.Jeff]

I was hoping that an earlier respondent would reply again with a bit more feedback on how the car performed after putting the l-Jet on a carby head.

As I’m doing a full restoration of the car whilst the engine is out I was planning on a full rebuild. Even though engine is low mileage and runs fine it’s been untouched from day one (why it’s was good buy) and needs a good clean up. Whilst engine is out plan is to optimise head, nothing radical just optimisation and running std euro cam. I’ve had an 81 previously and was more than happy with its performance only difference being it had twin DCNF’s. The std euro cam is very good.

My plan is to make the most of the Factory L-Jetronic and once I’ve got car back on the road change out the L-Jetronic for Microsquirt. I’ve just sourced a MkI Uno Turbo crank position sensor, cradle & pulley and apart from the pulley should directly fit onto the M202.15 block ready for the Microsquirt system. As I have A/C the pulley will need to be customised somehow so the pickup can sense TDC. But I’m not planning the Microsquirt changeover for a while mainly as I’d like to enjoy the car for a while and get used to it before starting to improve the injection side of things and all the extra work that involves.

If the L-Jetronic functions fine on std euro engine with what I’m planning with head wise optimisation and get close to 100bhp I’d be happy. Whilst I’d be overjoyed if it behaved as well as my ‘81 with twin DCNF’s I’d be surprised but happy to trade of some raw power for ease of use especially as my ‘88 X1/9 is air conditioned.

OK now that I have a better understanding of your planned engine mods, I think the FI will work without the need for a lot of changes. But it will be pushing it toward its safe limits. Previously I was getting the impression you were intending to build a more extreme engine, in which case I would not recommend the stock FI. Hope I did not confuse the issue, but that was why I asked for more info on your build plans.

Another question you may want to ask yourself is how you intend to drive the car and under what conditions. There are lots of parameters that will affect the load on the engine and the potential for detonation (pre-ignition or knock). The most extreme situations would be if you plan to racetrack the car vs a causal leisurely cruise. But even for normal road use, how hard you will push the engine and for how long (e.g. extended WOT periods), and at what RPM's. Also less obvious things like ambient temperature, carrying loads, operating AC, stop and go traffic, fuel grade, and more will play a role. A well maintained and properly tuned engine is important; ignition timing has a big effect on knock, cooling system condition effects engine operating temperatures - which also effect knock, etc, etc.

Keep in mind there is a difference between "it will work" and "it will properly maintain correct AFR's under all conditions without detonation". That difference will determine the reliability and longevity of your engine.

 

[Jefco]

Do you have any details regarding the “upgraded” injectors? Ie part number? Should be marked on the injector.
Thanks

I just checked my reciepts- they were Vick Auto PN 33-4699, apparently NLA.

 

[Dr.Jeff]

I just checked my reciepts- they were Vick Auto PN 33-4699, apparently NLA.

Were those the ones with the silver color body? If so they were a generic replacement for the Bosch injectors made by a another company. I don't recall the brand or exact specs off hand but there wasn't a huge difference in their rating, which is a good thing unless you can remap the ECU.

There are a few other Bosch injectors that can replace the stock ones with higher flow rates. Some were OEM for other applications and are about 30% greater capacity, others are universal part numbers with closer to a 50% increase. But keep in mind the ECU controls the injector "pulse" cycle duration and frequency, so just swapping injectors to bigger ones isn't the only change that's needed.

 

[Jefco]

Yes, silver body, non Bosch. They currently have something similar in appearance, but relative specs unknown, PN 33-4698; these are more than 50% more expensive, I got my set for $200.

 

[Dr.Jeff]

I have a set of those older version ones from VAS that came on a X I bought. That's why I happen to know what they were, I researched them a while back. I also have a set of Bosch injectors that I bought a couple years ago, and I see they are also much higher priced now.

Prices in general have definitely gone up noticeably in the last couple of years. Yesterday I was at a supply store where I'd purchased a wood panel about 2 years ago. The exact same panel (identical) from the exact same store is over twice the price now compared to then. I guess wood also gets the virus and therefore is in short supply. But the economy in general has not been good and inflation keeps creeping up.

 

[Stuartc]

OK now that I have a better understanding of your planned engine mods, I think the FI will work without the need for a lot of changes. But it will be pushing it toward its safe limits. Previously I was getting the impression you were intending to build a more extreme engine, in which case I would not recommend the stock FI. Hope I did not confuse the issue, but that was why I asked for more info on your build plans.

Another question you may want to ask yourself is how you intend to drive the car and under what conditions. There are lots of parameters that will affect the load on the engine and the potential for detonation (pre-ignition or knock). The most extreme situations would be if you plan to racetrack the car vs a causal leisurely cruise. But even for normal road use, how hard you will push the engine and for how long (e.g. extended WOT periods), and at what RPM's. Also less obvious things like ambient temperature, carrying loads, operating AC, stop and go traffic, fuel grade, and more will play a role. A well maintained and properly tuned engine is important; ignition timing has a big effect on knock, cooling system condition effects engine operating temperatures - which also effect knock, etc, etc.

Keep in mind there is a difference between "it will work" and "it will properly maintain correct AFR's under all conditions without detonation". That difference will determine the reliability and longevity of your engine.

Planning on full concourse rebuild Jeff.
Most likely used for club events and long country runs so car whilst be treated with care will be used.
Ultimately would love the twin-carb response of my old ‘81 X1/9 but the drivability that F.I. can offer especially with the A/C.
It’s hot here in Australia so driving with roof off is only early morning or late evening prospect unless you want sun stroke or cancer or both!

 

[Dr.Jeff]

Planning on full concourse rebuild Jeff.
Most likely used for club events and long country runs so car whilst be treated with care will be used.
Ultimately would love the twin-carb response of my old ‘81 X1/9 but the drivability that F.I. can offer especially with the A/C.
It’s hot here in Australia so driving with roof off is only early morning or late evening prospect unless you want sun stroke or cancer or both!

Sounds like it will be a nice build. I'm also in a desert environment so I completely understand the need for AC. And that adds to the engine load (compressor draw) and the cooling system demand (the condenser in front of the rad reduces the rad's efficiency). Both load and heat can lead to detonation, particularly if combined with too much ignition timing and/or too lean of AFR.

So let's say you are participating in a club event that involves some hard driving, in the summer with the AC on. The engine is under maximal demand due to the heat and workload. If your fuel or spark tune aren't correct then you will very likely experience knock...and eventually engine destruction. People that don't live in such hot climates like ours do not fully understand the impact it has on a car's engine.

As we've discussed, other parameters also have a role in detonation. High compression is a big one. So when you build your engine/head calculate what the final CR will be and determine if it is a safe level for your hot environment. Lots of blown head gaskets happen in my desert region. Make sure your cooling system is totally up to the task of maintaining a good engine temperature under the worst of conditions.

 

[fiatfactory]

Even though engine is low mileage and runs fine it’s been untouched from day one (why it’s was good buy) and needs a good clean up. Whilst engine is out plan is to optimise head, nothing radical just optimisation and running std euro cam. I’ve had an 81 previously and was more than happy with its performance only difference being it had twin DCNF’s. The std euro cam is very good.

Ok a couple of things you may or may not know...

You're 1982 australian spec car did not come with the euro cam, unless you replaced it....

Your 1986 GF may not have the 24/68 64/28 9.8/9.9 euro cam either... and as your engine is supposed to have never been opened up it will be kind of interesting what you'll find.

around that time Fiat seemed to increase the static compression of the 1500 engine for european conditions, it went from the large cast in fly cut pistons, to the small machined flycut pistons... just like a regata 85s carbed engine, still rated at 85hp, but has more static CR (9.5:1 as opposed to 9.2:1) and at the same time changes the cam to a more emissions friendly one (15/55) with approx 9.5mm lift.

So when you remove the head, if you find the engine already has small flycut pistons then it may not have the cam you're hoping for...

SteveC

 

[Stuartc]

Ok a couple of things you may or may not know...

You're 1982 australian spec car did not come with the euro cam, unless you replaced it....

Your 1986 GF may not have the 24/68 64/28 9.8/9.9 euro cam either... and as your engine is supposed to have never been opened up it will be kind of interesting what you'll find.

around that time Fiat seemed to increase the static compression of the 1500 engine for european conditions, it went from the large cast in fly cut pistons, to the small machined flycut pistons... just like a regata 85s carbed engine, still rated at 85hp, but has more static CR (9.5:1 as opposed to 9.2:1) and at the same time changes the cam to a more emissions friendly one (15/55) with approx 9.5mm lift.

So when you remove the head, if you find the engine already has small flycut pistons then it may not have the cam you're hoping for...

SteveC

Hi Steve

Pretty sure my old ‘81 was the euro cam as it was also a UK delivered car. I bought it off the original owner who imported it with him when he immigrated to AU. From memory we did verify the camshaft when I put the twin DCNF’s on. It was a great combo and you really had to keep an eye on the Rev counter as it would easily go off the end of the dial without hesitation.

You absolutely correct won’t know exactly what I have currently with this ‘88 until I strip it but the identification stamp on the head is “H” 7575664 which apparently is late 14 bolt 1500 SPI head, not sure what the “H” denotes? Would that indicate possibly 9.5 CR rather than 9.2?

My owners manual which came with the car says the camshaft is 24/68 64/28 and 9.2 CR so I can only go by that currently until I strip the head but I’ve never found Fiats paperwork to be incorrect in the past

Pretty much car is untouched from new, paint marks still on most bolt heads, even had original clutch but we change it out before exporting to Australia so customs couldn’t pick a fight re asbestos.