The TIG's 308 GTSi Conversion to EFI and Individual Throttle Bodies.

I haven't contributed to this forum before, but I do enjoy reading forums and I'm sad many of them have been dying out so I decided I should probably share and do my part to keep them going.

This project started with a completely OEM US market 1981 308 GTSi that I initially wanted to change to look more like a Euro spec car with the smaller bumpers and lower ride height. But as I worked away I got more and more ideas in my head about what I wanted from the car. I wanted to keep it within the spirit of a classic but also wanted to update the car a little bit. The sounds of a classic Ferrari with weber carbs were what I was looking for, and an exhaust without the restrictive thermal reactors. But I didn't want the hassle of messing with carbs, I've been there. So I decided that since I have more experience tuning cars with a laptop that I should probably build myself an EFI system and use some individual throttle bodies to get the induction sound I was looking for.

So I did what anyone considering this type of project should do. I spend a couple days doing a quick and dirty ITB conversion on a different car first to see if I had any business trying it my Ferrari. So I chopped up a Miata manifold and a Toyota manifold, did some milling and welded the two halves together, then some die grinder work inside to make the runners transition smoothly, machined up a throttle cable pulley, did a couple small changes to the wiring of the TPS and settings in my MegaSquirt ECU and got to tuning. It's a different strategy tuning for ITB's than with a shared plenum, but I quickly got it running and I would datalog and adjust my tune every time I took it for a drive for the next couple week. I quickly found my Miata was much more fun to drive, it was more responsive, it feels faster, but most importantly is sounds way better! The decision was made to proceed on the 308.

I thought I'd start this thread by sharing a little clip of what it sounds like running, then if some people are actually interested I can share some more detail on how I got here and where I'm going with it.

 

1. Custom CNC billet intake manifolds, designed with the help of a friend, but everything else I did myself in my garage.
2. Currently using TPS only, but I have a MAP wired in as well for future tuning if I want to use it.
3. Custom trigger wheel that fits on the crank pulley for the crank angle sensor. A second MAP sensor set up on cylinder one instead of a Cam angle sensor.
4. When I first started with stand alone ECU's I wanted something that local tuning shops and friends were using if I ran into trouble, they also made a plug and play for my first project so I didn't have to wire it in. Now I have experience on multiple vehicles and know how to use many of the Links great features and software. Link also has a lot of information in the help section, it's not always the easiest to find what you want, but it's likely there.
5. Instead of doing coil on plug I went with 8 remote mount coils. I messed around trying a few coil on plugs and found it was too inconvenient for servicing on the front cylinder bank. And really I wanted to look a little more time period with the plug leads visible.
6. The original fuel pump is in its original location, but I added an adjustable fuel pressure regulator.
7. I added 2 GM MAP sensors (one as described in number 3.), 2 Bosch knock sensors, 2 AEM wide band oxygen sensors (one per cylinder bank and connected through to the Link by CAN BUS for faster data), GM coolant temperature, AEM open element intake air temperature sensor, Hayabusa ITB TPS), Toyota crank angle sensor. When I built my harness I also included some wiring for fuel pressure and oil pressure and temperature if I ever decide to add that data. The oil Ferrari pressure light sensor, speed sensor, also send data to the ECU.
8. Injectors are OEM Hayabusa 260cc injectors. I have not been able to find that actual data for these injectors but I got some data that works from a Hayabusa specialist. At some point I want to pull the injectors and measure the flow as well as verify the deadtimes with my oscilloscope at different voltages.

 

Wow, it is nice to see you have some interest in my build, I've been following yours for quite some time. Amazing work! I have been sent multiple links by many people to your build. I'm not sure you'll learn as much from me as I could from you. But I'm happy to share what I know and help out others.

 

Part of my goal with all of my work on the 308 is to not change anything that I can't change back to OEM and to keep all the original parts in case a future caretaker of the car would like to go back to all original. I'm not really sure who would want to make the car heavier, less pretty (in my opinion), less responsive and less powerful. But I'm one of those picky people that would want all the original parts with the car too. So as I built parts or did wiring I found ways off attaching to the existing mounting points or connecting through existing harness plugs etc when I needed to use existing components.

So I started by removing the complete K-Jetronic fuel injection system except for the electric fuel pump, as well as the original ignition system including the distributor, coils and the Digiplex boxes and the complete engine harness. Next up one of my good engineer friends offered to do some 3D scanning of various parts and design my manifolds for me. I prefer to do everything myself but with the space limitations I thought it would be more effective to get some help with this part instead of welding up a set of manifolds that probably wouldn't fit or flow as well. Once we were happy with the design on the screen we thought it would be a good idea to test fit some 3D printed prototypes to make sure things fit as planned. Then I had a set of billet aluminum manifolds machined up on a 5 axis CNC and they turned out great and bolted up as planned.

With most of my projects I prefer to use as many available production parts as I can from other vehicles as I find OEM parts are often better and more reliable than aftermarket ones. Originally planned to use Toyota ITB's but I found they were too bulky and it was going to be difficult to figure out how to integrate injectors easily. So I ended up deciding on two sets of first generation Hayabusa throttle bodies, they are more compact, had injectors, fuel rails and TPS already integrated and they were easy to separate and separate in the middle to make room for the coolant hose connections needed for the heads. I also determined that if one Hayabusa set up could flow enough air and fuel to make 200hp then two sets will have more than I will need for a naturally aspirated 3.0L engine. They were fairly inexpensive to buy especially when you consider they came with injectors and TPS. Another benefit is different injectors and velocity stack options are already available from multiple vendors. I want the engine to look like it could have come from the factory when I am finished so I decided to mount the ITB's with the fuel rails, injectors and wiring tucked in the middle of the two banks.

Hayabusa ITB's on the left, Toyota on the right. Image Unavailable, Please Login

An early rendering to see what kind of space we have since I eventually want to build a proper air filter housing and have everything fit under the hood. Image Unavailable, Please Login

Perfect fit. Now to hide them with everything else piled on top.
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In this image you can see where I have machined spacers in the middle of each pair of ITB's as well as longer hard fuel line sections and modified the mechanical linkage between them.
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Thank you, this was my number one goal so I'm a very happy man.

 

It was an easy and expensive process. The easy part was having my friend do all the computer work, uploading a file and charging my credit card. It was hard waiting to see my fancy new parts. And it was expensive paying the credit card bill. I try to support local businesses but even they said it would be a fifth of the price if I just had it done through on online service and have it made overseas. It still cost me about 2K in Canadian dollars for the pair delivered to my door, so for my American friends you're probably looking at a fifth of that!

ITB's are easier to tune with TPS because it's hard to get a good MAP signal after your throttle is partly open. Sometimes you can use a blend of MAP with little load and idle, and TPS at higher loads and higher RPM when the MAP isn't reliable. Some tuners with more experience may disagree, there are different strategies when it comes to tuning, ITB's are tricky, but I like a challenge and I like learning. With ITB's especially I like to use the ignition timing features to control idle, it responds quicker than an idle air control valve and much easier to get a smoother idle with a more aggressive cam. I had an idle air control valve on the 308 but found I didn't need it once I set up idle with just the ignition timing so I have removed it for simplicity.

 

You are correct that it is a 0-5V signal and there is a little set up as far as how much change it looks for to keep the signal reliable and the ECU figured it out. It only needs the signal to determine what cycle the engine is in, the engine position is still determined by the crank angle sensor according to Link. My understanding is this is a new feature on the G4X series of ECU's. I am running a Link G4X Extreme, I have an older G4+ Extreme in another vehicle and it does not have this option. As far as wide open throttle I cannot say yet as the car isn't fully finished, tuned or been driven more than up and down my driveway. But I assume from talking to Link and them offering this feature it shouldn't be an issue at WOT.

 

That sounds like a neat solution and if I run into issues I may want to add something like that. I've been daily driving my Miata for almost two years on the ITB's running on the TPS and never had any issues, it drives great, makes more power and gets better fuel economy than it did when completely stock. So I feel pretty confident that it will be fine on the 308 especially since I won't be driving it unless there are nice conditions anyway. There is still a MAP onboard in the ECU to compensate for altitude etc in its fuel calculations.

Are you running 12 individual MAP sensors?

 

I got the engine running and decently tuned to start, idle, rev with no load, drive up and down my driveway and I am satisfied that my custom set up works. The engine is currently out and I have some upgraded parts and cams ready to go in. But I have tuned other cars with aggressive cams that didn't want to idle nicely until I got the idle ignition timing set up.
I have barely driven my 308 since I got it and the idle was always a little bit off and I had a little trouble getting it to idle nicely with my new set up and the AFR's were a bit different between banks, it was confusing me why. Until I disassembled the engine and found that the valves were all set too tight, one cam was about 1 degree out of spec, two were roughtly 10 degrees and one was 40 degrees out! I was surprised it would run and that it didn't cause any damage. The bank that was way out would sputter and pop and it got worse when it got warmer, I think I know why!

 

I am using the ignition timing for everything in the 308, if it was a daily driver I might do things a little differently. In my Tacoma I have swapped in a 1UZVVTi and I use a combination of DBW and ignition timing to control idle speed. You mentioned pulling timing to get your idle speed down, is that in your main ignition table at the speeds you want to idle? Or do you have separate ignition settings for idle timing like I do?

The Link ECU has pretty good resolution in the fuel and ignition tables so I have set the increments very close together at low throttle and then much bigger increments as the throttle opens.

I'm still sorting out the last of the details on the engine bits, nothing too exotic, but it should be a little spicier, I'll share more once things are finalized and going back together. The engine is in the cue at the machine shop.

Here's a shot just incase anyone ever wanted to see a Ferrari engine in a Lexus.
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The Link ECU can do quite lot, there are also ways of using virtual inputs and outputs and the math functions to do things that are not already selectable features. Customer service on their forum is great too, I've even seen them do some custom programming changes for certain engines or issues people are having

The ignition idle control in the Link has a few parameters to set up for how it functions and also what conditions have to be met to turn it on. You can download their software for free and have a look around and read the help section, it might give you some ideas. I'm starting to sound like I work for them, but I don't. I've been really happy and always been able to sort out whatever I've needed to without too much issue.

The ignition base timing timing on mine is quite retarded, it was last at -12.5 ( or 12.5 ATDC), then the ECU will constantly compare the engine speed to the target and add or subtract timing within a range I set many times a second to keep the engine speed close to target. I also found a small leak in my IACV set up when I took it part so the timing probably won't have to be quite so retarded when I put it back together. With the reading and videos I've seen it's not that uncommon to have such retarded timing with ITB's at idle.