Turbo systems for X1/9's

I would say they are all similar, except that ones in the head itself would heat soak more so than the T/stat location when the engine is off, simply due to the bulk of aluminum it sits in. The coolant temp passing over the sensor when running is going to be the same in the head as in the T/stat housing, it is situated in the coolant flow path regardless of T/stat flow to rad regulation.
 
Following my last post I was doing a little work on the head, with it off the engine and stripped down. I noticed something interesting when blowing compressed air into each of the two coolant sensor ports on the side of the head. Although they are located right next to each other, they are not connected. Compressed air blown into each one results in the air escaping from different coolant ports around the head (as compared to the other one). In other words, the internal coolant passages are not one big hollow chamber connected throughout the head. By blowing the air into several of the openings, it seems to actually be a few separate chambers. But there are some small common passages between them, because a little bit if the escaping air did transverse from one to the other. No idea why, possibly to direct the coolant in certain pathways to prevent hot spots? However I don't see how it would affect any of the temp sensors significantly.
 
This is an aside of a set of parts which would allow more modern injectors to be used with our standard intake manifold and existing fuel rail approach on an X.

For most modern stand alone injection systems they use injectors which are high impedance versus the low impedance used in the Bosch L Jetronic system Fiat adopted in 1980.

Later Bosch changed the L system to use the other injector style (found on BMW, Volvo and others) which still had a flexible hose supply, barbs etc. Of course the choices are limited in terms of fuel flow and so on as well as they are just plain old.

There is an adapter available which allows a flex hose supply with later mount type injectors:
https://www.efihardware.com/products/2358/14mm-Injector-Oring-To-Hose-Tail-Adapter-Steel

This doesn’t solve for mounting the injector into our manifolds (I haven’t done any research into that) but its at least one part of the solution.

Cross posting this in a few relevant threads to leave a crumb for others to follow in the future...

E5CD0A15-87DB-40B4-BE9C-9369FBBC804C.jpeg
E6F5CA22-5DE4-48B3-B958-0EB2CD51082F.jpeg 5D759D89-C047-433A-921F-CE561C5C5733.jpeg E6F5CA22-5DE4-48B3-B958-0EB2CD51082F.jpeg
 
I wanted to find high impedance injectors for a particular ECU application (more about ECU's later), so I did some research on this. Unfortunately it gets rather involved.

The intake manifold needs to be modified to fit 'modern' (high impedance) style injectors, where they mate with the small ports on the runners. That will involve machining and welding, plus more adapters and different seals. Then there is the matter of the length of the injectors. The design of our manifold, with the plenum directly over the fuel rail, does not allow for any additional length to fit under it. A lot of the high impedance injectors I came across were longer than our stock ones, with the adapters adding to the length. There are some "mini" injectors that might work, however their selection is even fewer (and cost higher). I also looked into using a different fuel rail but the same challenges existed, plus it also added to the overall cost.

The injector's fuel output rate was another issue. Most of the modern injectors are actually too big (flow) for our little engines. So finding the right combination of injectors (size, configuration and specs), adaptors, manifold modifications, seals, electrical harness connections, and getting the fuel flow rate needed all gets very difficult. Adding to the challenge, there isn't a ton of information available for the exact dimensions and other specs for many of the injectors out there. They are typically listed for replacements on certain applications. Trying to cross reference things got silly. Most of the sources I found had incomplete info and was contradictory with other sources. Frustrating and very time consuming with little results.

I'd love to find that unicorn injector part number, right selection of additional parts, and specific mods needed. Hopefully someone with more resources than me can come up with it. Although there is yet another factor to throw into this mix, cost. The price of modern injectors can be significant. Add to that the cost of the additional parts and services needed and it brings the already lofty price of the ECU, etc to new heights, far exceeding the worth of this to me.

There are a couple alternative approaches to this. One is to use a ECU that allows use of low impedance injectors. Many of the better ECU offerings have this capability. Unfortunately that comes at a cost, putting the overall expense back up there. Aside from the top of the line MegaSquirt products (also quite costly), the "affordable" versions (eg. MicroSquirt) do not allow for low impedance injectors.

The other option is to 'convert' low impedance injectors to high impedance ones by adding resistors. Several car manufacturers did this with their OEM FI systems for years. It allows for low impedance injectors (including the stock X1/9 ones) to work with lower cost ECU's that otherwise cannot run them. The drawback is it creates a slight time delay in the injector's response. But if you are programmed to run the FI with batch type firing, this really isn't an issue. Especially for a street driven car; it might be more of a factor if you are planning a extreme 'full race' engine build. And the lower cost ECU's like MicroSquirt will only run in batch mode anyway (the decision over batch vs sequential injection is another topic). In fact the MicroSquirt manual details the use of resistors for this purpose with the ECU.

Looking into the resistor issue I found a couple considerations. The impedance value of the resistor should be calculated for the specific injector to be used, such that it brings the total value close to the ECU's maximum capacity. The reason for this is to reduce the impact of time delay and to maximize the injector performance. Talking to the builders of the MicroSquirt units I was able to get some data to help with that. Running the ECU within a safe margin of total resistance, but closer toward the upper limits of that range, creates a slight amount of additional heat. So I purchased a aluminum heat sink to mount the ECU onto. Probably not necessary but why not.
The heat capacity of the resistor itself also needs to be high enough for continuous operation at that impedance value. The wattage rating and specific design and packaging of the resistor makes this possible, with the right choice. I've also purchased another aluminum heat sink to mount the resistors onto. Again, not necessary but I figure it will help with managing operating temps.
Finally the resistor needs to be a type that can conveniently be spliced into the electrical harness for the ECU.
Finding resistors that fit all of these requirements required some more research, but surprisingly the cost and availability of them wasn't bad once a specific part number was determined. The total cost for the resistors and heat sink was around $20.

My stock injectors have an unknown history and although inspection found them to be working, I decided to replace them for ones with a slightly higher output for my turbo build. Fortunately low impedance injectors are plentiful and very affordable. I found a direct replacement with 20% more capacity (perfect for my low boost turbo) at a very reasonable cost (around $20 each). Combined with the MicroSquirt's low cost, it puts the expense of using a aftermarket standalone management system into the realm of affordable for my low-budget build. This may not be the ideal solution. That decision will differ for each build's requirements, budget, application, and personal preference.
 
Last edited:
I wanted to find high impedance injectors for a particular ECU application (more about ECU's later), so I did some research on this. Unfortunately it gets rather involved.

The intake manifold needs to be modified to fit 'modern' (high impedance) style injectors, where they mate with the small ports on the runners. That will involve machining and welding, plus more adapters and different seals. Then there is the matter of the length of the injectors. The design of our manifold, with the plenum directly over the fuel rail, does not allow for any additional length to fit under it. A lot of the high impedance injectors I came across were longer than our stock ones, with the adapters adding to the length. There are some "mini" injectors that might work, however their selection is even fewer (and cost higher). I also looked into using a different fuel rail but the same challenges existed, plus it also added to the overall cost.

The injector's fuel output rate was another issue. Most of the modern injectors are actually too big (flow) for our little engines. So finding the right combination of injectors (size, configuration and specs), adaptors, manifold modifications, seals, electrical harness connections, and getting the fuel flow rate needed all gets very difficult. Adding to the challenge, there isn't a ton of information available for the exact dimensions and other specs for many of the injectors out there. They are typically listed for replacements on certain applications. Trying to cross reference things got silly. Most of the sources I found had incomplete info and was contradictory with other sources. Frustrating and very time consuming with little results.

I'd love to find that unicorn injector part number, right selection of additional parts, and specific mods needed. Hopefully someone with more resources than me can come up with it. Although there is yet another factor to throw into this mix, cost. The price of modern injectors can be significant. Add to that the cost of the additional parts and services needed and it brings the already lofty price of the ECU, etc to new heights, far exceeding the worth of this to me.

There are a couple alternative approaches to this. One is to use a ECU that allows use of low impedance injectors. Many of the better ECU offerings have this capability. Unfortunately that comes at a cost, putting the overall expense back up there. Aside from the top of the line MegaSquirt products (also quite costly), the "affordable" versions (eg. MicroSquirt) do not allow for low impedance injectors.

The other option is to 'convert' low impedance injectors to high impedance ones by adding resistors. Several car manufacturers did this with their OEM FI systems for years. It allows for low impedance injectors (including the stock X1/9 ones) to work with lower cost ECU's that otherwise cannot run them. The drawback is it creates a slight time delay in the injector's response. But if you are programmed to run the FI with batch type firing, this really isn't an issue. Especially for a street driven car; it might be more of a factor if you are planning a extreme 'full race' engine build. And the lower cost ECU's like MicroSquirt will only run in batch mode anyway (the decision over batch vs sequential injection is another topic). In fact the MicroSquirt manual details the use of resistors for this purpose with the ECU.

Looking into the resistor issue I found a couple considerations. The impedance value of the resistor should be calculated for the specific injector to be used, such that it brings the total value close to the ECU's maximum capacity. The reason for this is to reduce the impact of time delay and to maximize the injector performance. Talking to the builders of the MicroSquirt units I was able to get some data to help with that. Running the ECU within a safe margin of total resistance, but closer toward the upper limits of that range, creates a slight amount of additional heat. So I purchased a aluminum heat sink to mount the ECU onto. Probably not necessary but why not.
The heat capacity of the resistor itself also needs to be high enough for continuous operation at that impedance value. The wattage rating and specific design and packaging of the resistor makes this possible, with the right choice. I've also purchased another aluminum heat sink to mount the resistors onto. Again, not necessary but I figure it will help with managing operating temps.
Finally the resistor needs to be a type that can conveniently be spliced into the electrical harness for the ECU.
Finding resistors that fit all of these requirements required some more research, but surprisingly the cost and availability of them wasn't bad once a specific part number was determined. The total cost for the resistors and heat sink was around $20.

My stock injectors have an unknown history and although inspection found them to be working, I decided to replace them for ones with a slightly higher output for my turbo build. Fortunately low impedance injectors are plentiful and very affordable. I found a direct replacement with 20% more capacity (perfect for my low boost turbo) at a very reasonable cost (around $20 each). Combined with the MicroSquirt's low cost, it puts the expense of using a aftermarket standalone management system into the realm of affordable for my low-budget build. This may not be the ideal solution. That decision will differ for each build's requirements, budget, application, and personal preference.
Have you looked into using a capacitive shunt across the resistors in order to improve the response time? I would think that this could be done pretty easily as long as the peak current of the driver is not exceeded.
 
Have you looked into using a capacitive shunt across the resistors in order to improve the response time? I would think that this could be done pretty easily as long as the peak current of the driver is not exceeded.
Please tell me more. This goes beyond my basic electronics knowledge, so you'll have to be very detailed and specific if possible. Otherwise I won't be able to follow it. :)
 
I wanted to find high impedance injectors for a particular ECU application (more about ECU's later), so I did some research on this. Unfortunately it gets rather involved.

The intake manifold needs to be modified to fit 'modern' (high impedance) style injectors, where they mate with the small ports on the runners. That will involve machining and welding, plus more adapters and different seals. Then there is the matter of the length of the injectors. The design of our manifold, with the plenum directly over the fuel rail, does not allow for any additional length to fit under it. A lot of the high impedance injectors I came across were longer than our stock ones, with the adapters adding to the length. There are some "mini" injectors that might work, however their selection is even fewer (and cost higher). I also looked into using a different fuel rail but the same challenges existed, plus it also added to the overall cost.

The injector's fuel output rate was another issue. Most of the modern injectors are actually too big (flow) for our little engines. So finding the right combination of injectors (size, configuration and specs), adaptors, manifold modifications, seals, electrical harness connections, and getting the fuel flow rate needed all gets very difficult. Adding to the challenge, there isn't a ton of information available for the exact dimensions and other specs for many of the injectors out there. They are typically listed for replacements on certain applications. Trying to cross reference things got silly. Most of the sources I found had incomplete info and was contradictory with other sources. Frustrating and very time consuming with little results.

This is not that complicated. Getting the runners modded to accept standard Bosch injectors (e.g. 0280155746) is easy enough. The aluminum weldable bases ("weld in bung") can be bought off eBay. A universal billet rail can be bought by the foot, Summit, etc., then get it drilled to meet your injector spacing. All you have to do then is weld standoffs for the rail on the runners. The whole business fits easily under the stock plenum. I use 20lb injectors for the NA setup. Readily available size as they are used on many stock setups. You'll probably want 25-30lb (e.g.0280155759) injectors for a light pressure turbo setup.
 
Last edited:
Please tell me more. This goes beyond my basic electronics knowledge, so you'll have to be very detailed and specific if possible. Otherwise I won't be able to follow it. :)
The voltage across the capacitor in parallel with the resistor cannot change instantaneously so when the ECU fires the injector, it is essentially looking at the impedance of the injector itself w/o the resistor and supplies more current initially which should help the injector open quicker. The larger the capacitor, the more significant the effect. I would select a value that provides the extra initial jolt for a small fraction (10%??) of the injector duty cycle so as not to overload the ECU's injector drivers.
 
Assuming I follow this correctly, one potential consideration might be the selected value of the resistor. As I mentioned earlier it's value, along with the injector itself, is pushing the ECU's injector drivers toward their upper limits. If adding capacitors increases the total even more, then it would overload the drivers as you say. So the capacitor, resistor, and injector values all need to be considered together. Did I get that right?
 
This is not that complicated.
I guess what I was trying to say previously was the process involved to build what you described, and the additional cost it incurs, is more than I wanted to do. At least when compared to the simple and inexpensive alternative I chose. With the resistor approach the existing stock injectors could be used. However in my case I had already purchased new replacement stock style (low impedance) injectors with increased capacity (I was going to use another ECU that could drive them). Therefore I really did not want to buy more injectors, plus all the other stuff required. The total cost for the resistors and new injectors was less than one set of adaptors, not to mention everything else needed to use high impedance injectors. My goal for this project is to build a simple, inexpensive turbo addition to the stock X1/9 engine, with as few alterations as possible. In the case of someone wanting a standalone ECU but no turbo, the same system could be built retaining their existing injectors. Later I'll outline more details of the ECU I've selected and the other components related to its installation. I've been working on various aspects of this along with several other projects simultaneously so my progress has been sporadic.
 
Assuming I follow this correctly, one potential consideration might be the selected value of the resistor. As I mentioned earlier it's value, along with the injector itself, is pushing the ECU's injector drivers toward their upper limits. If adding capacitors increases the total even more, then it would overload the drivers as you say. So the capacitor, resistor, and injector values all need to be considered together. Did I get that right?
Right!
 
Those injectors would definitely work. I have to say though, I bought all 4 of my injectors for about the same price as one of these. But these really aren't a bad price, I just got a great deal on the others (but low impedance).

I really like your manifold mods. I'm sure that has a much larger throttle body on the end? Is the plenum just flipped around on the runners, or did you have to do some mods to mount it that way? I've never looked at how that would fit...great idea.

Also looks like some cooling system changes? One hose seems to be attached to the other side of the block?
Please post more pics of everything if you would.
 
Unfortunately to flip it around there's a lot of pie cutting and welding involved, I did it just to clear the engine cover for the prototipo which is really low.

Yeah there's an electric water pump in the system so I removed the waterpump housing and no thermostat.

3361A52C-1C91-4640-9050-83372A7D91DC.jpeg

9D64D1FE-F6AB-4364-B960-05A844070E06.jpeg

686F54FB-9659-4580-8880-C775EE7763B7.jpeg


The header tanks at the front there in the wing and the water pumps down bellow near the right front wheel.
 
Unfortunately to flip it around there's a lot of pie cutting and welding involved, I did it just to clear the engine cover for the prototipo which is really low.
Yeah there's an electric water pump in the system so I removed the waterpump housing and no thermostat.
The header tanks at the front there in the wing and the water pumps down bellow near the right front wheel.
Great build. The more I look, the more cool mods I see. By chance have you ever documented the whole build somewhere? I'd enjoy learning all the details.
 
Unfortunately I haven’t I sort of gave up trying to document everything. The amount of changes I’ve made over the cars development life is ridiculous. Other than it all being in my head so I could replicate it there isn’t really a guide or a list of everting per say. At one point the car went through an intercooler placement, type and design every 6 months just to get that part of it right.
 
I was thinking you had done some kind of electric hybrid until I realized the big-assed belts and cog wheels that can be seen under the car in one pic are most likely because the car is up on a chassis dyno!
 
Back
Top