[Mk2] [Turbo] new gearing

[loudandproud205]

Mine was quite tolerable at 144 in 5th was around 5800/6000 rpm IIRC

Kinda bottled it at that (as I was using the sat nav for speedo as the car one don't work)

[swaggansway]

lol, that's what I used to do till I fixed mine. hard and unnerving lookin at those lil digits on a sat nav ay! bit scary at that speed tho, feels like the car is floating

[greeny]

I have built myself a stupidly quick mr2. it is a rev1 with a rev3 converted forged engine. it is running 1.5 bar boost and totally destroys anything that tries including most bikes lol

Push bikes?

[swaggansway]

on a good day I can take a 21 gear mounting bike on!

[Marf]

its a ct20b, haven't changed fueling. a/f meter reads 20.0 when no throttle and about 8.0 under full throttle.

Tell me that you are not running a narrowband O2 sensor?!

Those readings are at the extreme ends of rich and lean, which indicate to me either your fuelling is way off(8:1 under full boost with pump fuel aint gonna run) or you have a narrowband sensor on there, which tells you bu88er all about how safe your on boost fuelling is.

[swaggansway]

like I said it'd an apexi, it works off the o2 signal from the ecu! is this no good?

[Marf]

like I said it'd an apexi, it works off the o2 signal from the ecu! is this no good?

In short NO

All the stock sensor will tell you is three things, and only one accurately

1) if you are at 14.7:1
2) if you are richer(by any amount) than 14.7:1
3) if you are leaner(by any amount) than 14.7:1

A narrowband sensor is only accurate when reading 14.7:1. This is the a/f ratio the ECU will try and reach when you are cruising off boost to give the best fuel economy/cleanest burn.

With a narrowband sensor, if the ratio is leaner than 14.7:1 then it'll read 20:1 as you're seeing. If its richer than 14.7:1 it'll read 8:1 as you're seeing.

This information is utterly meaningless. Your on boost fuelling may be richer than 14.7:1, but that may mean 13:1, which is way way too lean for on boost fuelling.

Never ever ever rely on a narrowband gauge to say your on boost fuelling is ok.

These graphs show how a narrowband and wideband sensors read.

Narrowband - the vertical line in the middle is 14.7:1, as you can see, either side of this its not accurate, it just tells the ECU that the ratio is richer or leaner than 14.7:1



Wideband



If anything is not clear, please ask. Fuelling(especially on boost fuelling) is far to important to be unclear about.

[swaggansway]

wow, that is informative! thank u

guess it is time to upgrade my a/f meter now

[Marf]

No problem

You'll wanna find out if you have an additional bung in your downpipe to screw in a wideband sensor.

If not you'll need to look at replacing your stock narrowband sensor with a wideband, then feeding the stock ECU the narrowband output from its control box so your cruise fuelling works properly.

Though ideally you want a new bung fitted at the bottom of your downpipe, widebands should be placed further from the turbo than the stock sensor:thumleft:

[JJ]

And turn your boost down, or you'll be rebuilding it again soon... !!

[swaggansway]

I did turn down as soon as u guys pointed out that I was being a xxxx but just too late, she when BOOM

[DiYMCRT]

if you can get hold of one get a Carlos sainz or RC celica box (st185 but must be the cs or rc version) they have looong gearing and 8500rpm in top with about 600 bhp is 200mph!! i had one when the 3S was in the rolla i had to lift at 175 mph (gps calibrated but there was loads to go to the red line.
you will need to put the gear set in your box along with your diff or swap the ring gear onto your diff and swap the selector over but the boxes are the same bar diff and transfer

fensport did this in their 3sgte corolla 200mph+ achieved (and the mr2 is more aerodynamic) but i don't think it's the entire gearset i was under the impression it was just the FD that needed to be changed

good look on finding one though

[swaggansway]

opening my gear box is gonna be like opening a can of worms. more complex than the engine I guess