Low 10s AFR - am I too rich?

[tommy10101]

Hi guys,
Check out this video of my laps at Combe the other day.

https://youtu.be/WxlVC-vec0o

If you look closely at my AFR gauge (in the middle of the 3 gauges) you can see I am around 10.1/10.2 AFR at full power down the main straight

I was also told the car was spitting flames when easing off for the Braking zones. Also, it just doesn’t feel as fast as I think it should do - I would guess it’s around 260/270 fly wheel hp when a lot of rev3 turbos with my mods are + 300.

the car is boosting about 16psi at initial full power and then tails off to 14 ish at redline. Manual boost controller and CT20b.

any thoughts or suggestions to improve my tune?

I was told 11.5 is the perfect AFR at full power. So am I down on power due to running too rich do you think?

[MR2DI4]

the car is boosting about 16psi at initial full power and then tails off to 14 ish at redline. Manual boost controller and CT20b.

Thats a bit weird, the CT20b is good for up to 19psi so it shouldn't be dropping off from 16psi. A manual boost controller is a bit low gain to avoid boost spikes so you potentially loose some midrange but eventually it makes no difference to the power at the top end as it should get to the peak and hold it if the MBC and Turbo are good.

I was told 11.5 is the perfect AFR at full power. So am I down on power due to running too rich do you think?

Peak power and peak torque occur at different AFR's. Mines still a bit rich I recon and its running in the 12's. If What you have is 11.5, thats not ideal power but its safe. All that extra fuel is cooling the intake charge.

No mention of what ECU your running.

[tommy10101]

Stock ECU, which is why it’s so rich I guess

Is there anything actually dangerous to the engine about running low 10s AFR WOT?

Ah didnt realise the extra fuel would cool the intake charge, that’s a nice positive

Yeh not sure why it’s not holding boost till redline. Maybe I should just turn up the boost slightly and see if that helps the AFR

[MR2DI4]

Nope stock AFR's are in the 10's under full boost depending on the rpm and engine loading.

Mine comes out of the 10's and 11's into the 12's depending on the variables. Exhaust is still excessively black inside on mine so its still rich.

Something is not right however with either the MBC, what MBC are you running ? or the Turbo itself is simply worn out and is not holding the boost.

Try increasing the boost, you still have a few psi to play with if its there. If you get a bigger peak but then drops back to 14psi again you have a problem.

[tommy10101]

It’s an Rspec manual boost controller, £30 from eBay. It said specifically it was for the mr2 turbo. It’s the ball and spring type

I am cautious to up the boost as I can see from my onboard video, on occasion it peaks on initial throttle to over 17psi on its current setting. But never above 15psi at redline.

Clearly there is enough fuel. Maybe an EBC would benefit here if I don’t want to go the whole way and go stand-alone ecu

It’s booked in at Surrey rolling road in a few weeks. Will be interesting to see the graphs

[tommy10101]

Plus the turbo is a recently refurbished ct20b with billet compressor wheel and the waste gate enlarged. The turbo should be good hopefully so I’m thinking it’s the mbc

[MR2DI4]

Usually those MBC's work just fine. Mine is a TRUST ripoff version and it was as cheap as chips but they appear to be as scarce as hens teeth. EBC doesn't make a huge difference and you can get 90% of the way there with an MBC and the power at the top end should be the same as an EBC, it should just level off at a stable boost and flatline there if both the MBC and the Turbo are good. Obviously its a whole lot easier to change the MBC so I would try something else.

Picture of mine here.

https://www.croooober.com/en/item/cpart ... Controller

Similar but this looks better quality than mine.

https://en.trust-power.com/uncategorize ... controler/

https://www.suprastore.com/gredtvulmanb.html

The genuine version is not cheap.

Could not be bothered going down the EBC path, its not so much the cost but the realization of what you need electronics wise. The controller needs to know a whole lot of variables to edge out the simple and very easy to setup MBC from RPM's, what gear your in, roadspeed, throttle position, boost pressure and multiport solenoids, you name it and I think this amount of grunt is best left in a factory ECU. Quite frankly a pneumatic actuator is a nightmare to control with a digital device thats either on or off like a solenoid and if it wasn't for the cost or the heat aspect in the engine bay its a job for a servo motor. The MBC is analogue, it keeps it simple if you get a decent one.

[Voivod]

Usually those MBC's work just fine. Mine is a TRUST ripoff version and it was as cheap as chips but they appear to be as scarce as hens teeth. EBC doesn't make a huge difference and you can get 90% of the way there with an MBC and the power at the top end should be the same as an EBC, it should just level off at a stable boost and flatline there if both the MBC and the Turbo are good. Obviously its a whole lot easier to change the MBC so I would try something else.

I never bought any boost controllers manual or electronic and will never buy...they are overpriced junk. You can set the boost manually and it will never fail as the electronic. The best safety design is when turbo wastegate operated by the vacuum.

[Voivod]

Stock ECU, which is why it’s so rich I guess


Ah didnt realise the extra fuel would cool the intake charge, that’s a nice positive

Running rich is not positive..I prefer running on leaner side for a few good reasons.If you were talking about EGR's then is a different story.

[MR2DI4]

Stock ECU, which is why it’s so rich I guess


Ah didnt realise the extra fuel would cool the intake charge, that’s a nice positive

Running rich is not positive..I prefer running on leaner side for a few good reasons.If you were talking about EGR's then is a different story.

I don't understand what your talking about. Running lean on your 3SGTE results in the engine going BANG. Toyota run it as rich as hell under the stock setup to compensate for possible poor octane fuel and all sorts of other variables getting worse over time like the fuel pressure and by doing so make the engine idiot proof so they don't get a load of engine failures coming back to bite them in the ar5e.

If you run lean the intake charge temperature rises and you risk knock and knock quickly destroys your engine.

You need to know exactly what your doing when you start playing with AFR's or it will all end in tears.

Do some research, peak power and torque occur in the 12's or richer there is no point running lean.

[Voivod]

I don't understand what your talking about. Running lean on your 3SGTE results in the engine going BANG

I know that we have some different points of views and disagreements but that's OK However just because I said running leaner you jump to your conclusions.(the engine going BANG) that's NOT entirely true. As I said I prefer to run leaner but that's doesn't mean the leanest when it will melting the edge of piston crown! p.s (I actually did that at one point but running far too much boost and timing and it took about 6000 miles before is happened on a brand new rebuild engine) Running leaner is far more efficient then running rich!

Toyota run it as rich as hell under the stock setup to compensate for possible poor octane fuel and all sorts of other variables getting worse over time like the fuel pressure and by doing so make the engine idiot proof so they don't get a load of engine failures coming back to bite them in the ar5e.

Yes they run rich as hell..but you failed to understand that those engines are from 90's and if you bothered to look at the evolution of 3sgte you'll find it interesting in many ways... from my point of view Toyota didn't done a Great Job at all

If you run lean the intake charge temperature rises and you risk knock and knock quickly destroys your engine

Again is a misconception or misunderstanding! Running lean Do Not Rise temperature in the intake charge! It's a vice versa..also knock doesn't quickly destroys your engine Don't confuse Detonation vs Pre-Ignition!

You need to know exactly what your doing when you start playing with AFR's or it will all end in tears.

If the 3sgte is lost then I would not shed a single tear for it!

Do some research, peak power and torque occur in the 12's or richer there is no point running lean.

We've been through that before..didn't we?

p.s Look don't take any offence! I'm really appreciate your input and your response and your effort..for the record you're the only one! Rest must be sleeping or bought Prius or something

[MR2DI4]

Sadly I think the numbers on this forum have really dropped off over the years. I just looked back at some of my really old posts and the people joining in are just not around anymore.

I guess its just the number of MR2's on the road continue to drop. We used to be flooded with them over here years ago and someone went into the car registrations and it was thousands but these days it must only be hundreds.

Its turning into a bit of a echo chamber on here.

[benckj]

Few of us old timers still lurking around. Just not into the mods like I was several years back or finally hit the sweet spot with my 2.

[TonyleFrog]

O/T. The drop off is primarily due to the relentless rise of social media. Also, when longer term members drift away from MR2 ownership the new blood, such as it is, doesn't tend to frequent this place which is a much better source of technical information than SM.

The latter does not function well as a repository and there are very few new questions under the sun which haven't been asked on here before. The search facility will normally unearth the answers. It's just a matter of knowing how best to define the parameters.

The MR2 has been out of production for 14 years and the number left is continuing to decline.
There have been more Mk1s and Mk2s SORNed than are taxed for the last 6 years.
The UK stats are here - https://www.howmanyleft.co.uk/?utf8=%E2 ... toyota+mr2