stevenford_uk

i have had a search on here and cannot really find anything that properly explains what hybrid alpha n is, i have read about dual fuel tables, tps instead of map, tps as well as map, etc etc and now i am really confused.
can someone please explain to me how to run hybrid alpha n because i am installing my throttle bodies this coming week and i have read that i need to run at least alpha n instead of speed density because of the wild variations in map readings.
thanks

mschlang

It is a strategy that uses alpha-n at idle and MAP sensing otherwise. Mostly used with wild cams that have too much MAP variation at idle to fuel properly. I tried it for a bit with my mustang and didn't find much of an improvement.

arga

Let's hear some details on those throttle bodies. DIY? If so I'd appreciate some info oh how you fabed the manifold. I have a set of 98 GSXR 750 throttles sitting next to me and no idea how to make them work.

I was going to point you to http://www.msefi.com/ but I ran a search and you were the first two posts to come up. At this point it looks like you know more than I do.

cjernigan

iTrader: (13)

https://www.miataturbo.net/forums/showthread.php?t=6528

Largest amount of info on this I have seen on mt.net

stevenford_uk

here are some pictures from the first day i got the bodies, with the standard intake manifold.



i cut the manifold where the straight webs are just past the mounting flange, made up some billet ally runners in the lathe, pressed them to the shape of the ports on the intake manifold side of things whilst keeping them round on the throttle body side, got them welded on.
once they were welded on there were massive steps inside the manifold so took a die grinder to them and ported it right out and the profiled the inside of the manifold with chemical metal and ported that to suit.
then the throttle bodies needed modifying to suit, i used the standard mx5 injectors and fuel rail, so i tapped the injector holes on the throttle bodies and inserted some pipe takeoffs for the vacuum log for the brakes. the takeoffs were just 10mm bolts that were machined down and drilled with a 5mm hole, then screwed in and araldite'd into place.
i am going to be using the standard fireblade bellmouths if they fit but i will come to that once i install them when my gasket kit arrives.
i have also put a manual adjuster where the fast idle valve used to be on the throttle bodies to conrol my idle.
and i had to modify the fuel rail pipes, just bent them out of the way and cut the one from the fpr.

i have made a vacuum log for the map sensor, so i can run the speed density algorithm at first, it should help to smooth out some of the fluctuations, and once i have wired in my tps i will be going over to alpha n, and once i have got my head round hybrid alpha n i will give that a go.

i will post up some pictures of my throttle body setup later once i have finished taking my mates engine out of his mini.

arga

Very interesting. Thank you.

I didn't realize the stock runners stayed oval that far up stream. I had considered modifying a stock manifold by boring out the runners an inserting sleeves with the sleeves extending out of the manifold about 2cm. I could then mount the inlet boots to the sleeves. If the runners aren't round then that won't work. It was a moot point for me anyway. The 99-00 and 01-04 manifolds' #4 runner makes a sharp S turn right after it leaves the head. I have though about modifying a 94-97 manifold. I still may just fab the whole thing it out of steel. At least I can work with that.

Be careful using chemical metal (JB Weld?) in the inside of your runners. If it brakes free, bad things will happen. Then again, if you took a die grinder to it and it didn't come loose it might be fine.

Have you seen the threads at Miata.net by ElyasWolff? He documents how difficult it was tuning IRTBs with speed density. He eventually went with alpha-n and was much happier. Might be better to start with alpha-n then move to hybrid.

That one post about using a .5mm restrictor on your map sensor was interesting. It sounds counter productive, though. One of the biggest attractions to IRTBs is throttle response. If your MAP, and therefore your fuel, is artificially limited then some of the benefit is lost.

stevenford_uk

the map line is not restricted, it comes from the standard map tappings on the irtb's then straight into a vac log to smooth out the fluctuations.
the vac lines for the brake servo come from 8mm bolts drilled out with a 5mm drill bit that are fitted into the bodies and then to a vac log then to the servo.
i dont expect to get it smooth with the sd tuning, i just want to get it running with that, then i can start on the tps.
can someone explain how to actually setup the hybrid system on megasquirt?
cheers

stevenford_uk

as promised here are the pics of my finished throttle bodies, apart from maybe the bellmouths.

ecugrad

You have to set it to TPS in the MT Setup. Then in MT under ADVANCED --> Advanced Code Option select Hybrid Alpha-N.

I have been down the road you are on now and am back to the stock Intake Manifold. It just wasnt for me. I am actually trying to talk myself out of buying a used BEGI kit right now.

Good luck!!!

stevenford_uk

cheers matey, mucho helpful

arga

That's not what I wanted to hear. Day to day drivability not there? Too loud? Too much work for too little gain?

iWeasel410

Are you sure your throttle bodies and air horns aren't going to run into fuel lines or anything on the passenger side of the engine bay? I've been looking at designing my manifold (I already cnc machined the flange) and a lot of the flange->itb adapters for the miata angle the runners up quite a bit to avoid running into the under-hood accessories.

stevenford_uk

i trial fitted them today and the bell mouths foul the brake and fuel lines, so i am going to buy some stubby weber bell mouths and fit them instead.
on a slightly different note, about a week ago my car started bellowing out white smoke, and misfiring from cold, when warm she would still smoke blue and white but not loads, the other day it got that bad i decided it was time for a new head gasket, so i stripped off the head and to my surprise the head gasket looks fine, i compression tested it before i ripped it off and it was perfect, so now i am thinking it may have a crack in the head to cause that much white smoke. i am hoping its not, but can you guys think of anything else it could be???

also throttle bodies can never be too loud the noise is glorious!

ecugrad

You got it I also was not overwhelmed with touted "instant throttle response".

Plus I decided I'd rather have a new house with a garage, the sale of my ITB's sure has helped with the downpayment.

I'm the posterchild for life getting in the way of racing.