Please do not make sarcastic comments about selling and buying turbo to fix the problem. This may not be for me anymore, but there are a lot of people out there still interested in supercharging their mx5's and I'd like to help them on their journey if this is the path they choose to take
Some background on my setup:
I have a 1990 NA6 mx5. I had it on Megasquirt DIYPNP2 standalone engine management with an Innovate LC-1 wideband and GM IAT sensor (no AFM and no TPS, using MAP) and 550cc RC Injectors.
The car was running with an Eaton M45 supercharger pulled from a JCW Mini and had a 9PSI reduction pulley put on. I ran the supercharger with a recirculation valve, two throttle bodies (stock and one between charger and filter piggy backed together with a second cable), and a front mounted intercooler.
When running this setup I found that there were too many compromises to cope with so I returned it to n/a and back on standard management for reliability (sold my daily).
First off, I found that although the motor felt like it had some decent torque to it, it wasn't very responsive through the rev range and often felt like I had a very heavy flywheel. I'm assuming most of that came from poor tuning but also extra load on the crank pulley from the supercharger too?
Secondly and worst of all, it screamed regardless where you revved it in through the range. From 2000rpm to 7000rpm the charger would scream at you in your face which became almost unbearable. I let a friend take it for a drive and I could hear it nearly 2kms away...
I'm leaning to selling this setup and moving down the turbo route, but for curiosity sake I'm interested in finding a few things out.
I did some brief research and found out the JCW Mini's ran at 11.6psi from the factory and lots of people push the boost up to 14psi. Most videos you watch and in real life if you get the opportunity to hear, they don't start to whine loud until you are on wideopen throttle midway through the rev range. I find that odd since mine sounded like it was on WOT pretty much right through. and When on WOT it was even louder again at 9psi.
I have a friend with a similar setup that runs at 5psi stock boost but you don't hear the charger until around 5500rpm.
So what could be causing this?
The next question I have is about running dual throttle bodies. Ages back when I first set this up I read over and over that the key to a smooth idle is having dual throttle bodies to help regulate it. To me this seems overly complicated and I'm wondering whether it would be easier just having a single throttle body at the supercharger and deleting the one at the supercharger. Is there anything I should keep in mind with this? The main reason for me wanting to use just a single throttle body is because when using two piggy backed, the pedal becomes very firm and resistive to push. This is because both TB's are sprung and you are pushing against 4 springs (two springs in each throttle body used to make it snap shut when off throttle).
I've heard (complete speculation on others and no facts I can find to prove it) that the recirc valve I have may be making the charger louder. I don't really see how this is possible but if anyone wiser can shed some light on it that would be great. Any sense deleting it and just using a blow off valve after the intercooler?
Lastly, I've been thinking about the best way to run this. I've been told by a tuner that one of the biggest problems I have with throttle response comes from the overly long pipes used for my front mount intercooler. Since I had aircon at the time, there was a lot of dodging involved and as a result, pretty long intercooler pipe. The Eaton chargers were designed (from what I've read) to be run intercooled, especially at higher boost. I've felt how hot it can get too. So I'm wondering it a V-mounted radiator might be a good idea so I can place the intercooler on top. This will allow the supercharger to use the shortest amount of pipe possible between the inlet manifold and the supercharger.
If don't correctly with an appropriate sized intercooler it shouldn't be much longer than a cross over pipe one would use in a non-intercooled setup.
To me it seems feasible but has anyone tried it?
I apologies if this has been covered in another thread. I had a look but didn't see anything at all. Infact there are only a few threads in this section for some reason (that I can see anyway).
Reason I made this thread is because I really wasn't thrilled with my supercharger setup and want to know if this is just how it is or if there is a way to fix all this and have something I can enjoy. I still haven't sold the gear so putting it on again is a possibility still.
It was fun at first when I had it running but the noise was the biggest cop magnet and in Australia having a modded car is like raping a kid in the eyes of highway patrol.
If I could have this running quieter and more responsive, I'd be happy.
Feel free to shoot me any questions about my setup that I may have missed, and that will give you a clearer picture. Unfortunately I have no photos but if I can grave dig one, I'll post it.
)
