Huw
Club Member
With the car in storage for the winter and in need of some car fettling, I thought I would start a little experiment thread to see how far I can push the performance of the stock EFI system before it needs upgrading. I want to keep the engine looking as stock as possible (I might have blown that with the over application of blue silicon hoses and gold zinc coatings) but squeeze as much extra performance out of the original components before having to replace the ECU and everything else. Replacement of the EFI system with a modern ECU and gubbins would be a far easier path to performance upgrades, but where is the fun in that!
Having upgraded the distributor, cam, head and exhaust system already, I will be looking to improve air flow into the engine and improve the range of fuel mix, currently only fine adjustment to enriched or lean the mix.
1. Breathe
So first off I want the ZX to breathe a little better. The current inlet manifold runners are highly restrictive and one of the biggest bottle necks for air flow. Opening them up isn’t possible as the castings is so thin, the only answer is to replace the stock inlet manifold with a performance one but that will mean upgrading the ECU as the stock one doesn’t play well with improved air volume. Plus that would break my ‘keep it stock look’ experiment. So rather that increase the volume I’m going to see what improved flow will do for the engine. I will touch on air filters later.
l also want to get the throttle response a bit snappier. A nice (not silly) big throttle body should help. Contrary to popular myth a big throttle body will not create extra horses for this set up, but it should make the throttle response better. With that in mind I have got a Borla 60mm throttle body cheap off eBay. It needed some modification to allow a take off for the valve case breather and a bypass for setting the idle. Just need to make a bracket to mount the throttle position switch and it’s ready.
Next on the list is to improve the airflow within the manifold. Having spent hours porting and polishing the head, Im going to smooth out the internal surfaces of the inlet. So I have got a turbo inlet from a kind forum member (thanks Steve) as the runners are slightly bigger. It’s all marked up and ready for surgery. Need to cut it open to smooth out the castings and plug unwanted bolt holes. Also going to cut off and seal up the anti smog channel. Once smoothed and polished, it will be brazed back together as it’s easier than welding. Only one thing left undecided, do I remove the webbing between the runners or keep them. Removing them should help reduce heat-soak but will detract from the stock look.
So let the cutting beginning!
Having upgraded the distributor, cam, head and exhaust system already, I will be looking to improve air flow into the engine and improve the range of fuel mix, currently only fine adjustment to enriched or lean the mix.
1. Breathe
So first off I want the ZX to breathe a little better. The current inlet manifold runners are highly restrictive and one of the biggest bottle necks for air flow. Opening them up isn’t possible as the castings is so thin, the only answer is to replace the stock inlet manifold with a performance one but that will mean upgrading the ECU as the stock one doesn’t play well with improved air volume. Plus that would break my ‘keep it stock look’ experiment. So rather that increase the volume I’m going to see what improved flow will do for the engine. I will touch on air filters later.
l also want to get the throttle response a bit snappier. A nice (not silly) big throttle body should help. Contrary to popular myth a big throttle body will not create extra horses for this set up, but it should make the throttle response better. With that in mind I have got a Borla 60mm throttle body cheap off eBay. It needed some modification to allow a take off for the valve case breather and a bypass for setting the idle. Just need to make a bracket to mount the throttle position switch and it’s ready.
Next on the list is to improve the airflow within the manifold. Having spent hours porting and polishing the head, Im going to smooth out the internal surfaces of the inlet. So I have got a turbo inlet from a kind forum member (thanks Steve) as the runners are slightly bigger. It’s all marked up and ready for surgery. Need to cut it open to smooth out the castings and plug unwanted bolt holes. Also going to cut off and seal up the anti smog channel. Once smoothed and polished, it will be brazed back together as it’s easier than welding. Only one thing left undecided, do I remove the webbing between the runners or keep them. Removing them should help reduce heat-soak but will detract from the stock look.
So let the cutting beginning!
