A turbocharged engine is a double-edged sword. Extra energy is available by way of extra increase, however so is extra catastrophe.
So, even if you’re vaguely contemplating turbocharging an engine, plan to at the very least monitor the opposite elements that might be affected by the extra air. Most notably, this implies maintaining a tally of how a lot gas will get blended into that flamable fog being rammed into your cylinders.
The connection between gas and air in your engine is multifaceted. On one hand, you might have one thing referred to as the stoichiometric ratio, which is the perfect combination of air and gas that, when combustion happens, leads to no leftover gas or its catalyst (oxygen, on this case).
[Turbo boost is good, but too much can be bad]
For typical gasoline, on Earth, the place air is about 21% oxygen, that ratio is 14.7 components air to 1 half gas. After all, totally different gasoline blends and elevations have an effect on this quantity barely, however that’s the baseline.
However that 14.7:1 ratio doesn’t inform the entire story of max potential. See, when you could also be burning the entire gas at that ratio, secondary results may very well be robbing the engine of most energy. Full burning of the gas means much less atomized liquid gas within the combustion chamber, which suggests much less cooling of inside combustion surfaces, which suggests extra power misplaced as warmth, for instance.
Now, each engine is totally different, and most make most energy at some ratio that isn’t the perfect 14.7:1, however this ratio is barely attainable by way of dyno testing and exact monitoring. In case you have a contemporary automobile, the monitoring half is often so simple as slipping a connector on the OBD port and utilizing some software program or a {hardware} logger to learn the info being despatched to the onboard laptop.
However our 1991 Toyota MR2 Turbo has no such trendy accoutrements, and the manufacturing facility oxygen sensor that sends exhaust knowledge to the onboard laptop is extraordinarily low-resolution.
Time for Some Sensorship
The answer is a correct wide-band oxygen sensor, which often means the set up of an accompanying in-dash gauge or monitor to maintain monitor of the numbers. However we discovered a neater answer that installs in minutes from Performance Electronics. The corporate’s PE-Wideband equipment consists of a Bosch sensor that connects to a Bluetooth-enabled controller you’ll be able to monitor through an app in your iOS or Android machine.
The setup simply requires an influence and floor connection, so all of the wiring can keep beneath your hood–or engine cowl, in our case. The unit additionally has CAN inputs and outputs and a 0-5v output to attach it to devoted gauges or your programmable ECU.
Set up on our MR2 was a snap, as we’d simply put in a TCS Motorsports downpipe that we had the foresight to order with an additional oxygen sensor bung already put in. We merely eliminated the plug, put in the brand new sensor, and plugged it into the unit. We have been up and working inside half-hour. The equipment additionally comes with a weld-in bung fabricated from delicate metal in the event you don’t have already got an out there and keen bunghole. Stainless bungs can be found as nicely.
The app is straightforward to make use of, has real-time monitoring and a few primary logging options, and reads AFR both as ratio or lambda. Typical AFR exhibits excellent as 14.7:1, with decrease numbers–which means extra gas per air mass–indicating a “wealthy” situation and better numbers indicating a “lean” situation. Lambda expresses excellent stoichiometric ratio as 1, with readings decrease than 1 indicating wealthy and better than 1 indicating lean.
So now that we are able to simply monitor our air/gas ratio, what will we do about it? Effectively, first off, it’s good to know that our engine is correctly metering gas.
At wide-open throttle, the onboard ECU richens the combination to round 11:1, which suggests a variety of unburned gas–but additionally a variety of security margin for not producing extra warmth or preignition, which may shortly kill an engine. As we add increase and open airflow, making certain the gas combination is throughout the protected zone might be further insurance coverage towards untimely catastrophe.
But when we in the end wish to take advantage of energy that we are able to for a given configuration and increase degree, we’ll want a solution to exactly regulate that gas combination at numerous load ranges. Sadly, in contrast to extra trendy ECUs, the MR2’s classic laptop is just not simply reprogrammable, so we’d want to put in an aftermarket engine administration laptop. For now, although, this setup is a welcome improve.
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An “out there and keen bunghole”? You guys are a riot.
That is an excellent article. Thanks.
SV reX mentioned:
An “out there and keen bunghole”? You guys are a riot.
That is an excellent article. Thanks.
I’d encourage individuals to get an information logging system, so that you’re not logging together with your eyes. Try to be driving.
And even on a dyno, a logging system will present you exactly the place the problems are as an alternative of making an attempt to juggle a/f, engine velocity, and a few load measurement.
I like for the eu to simply do all of the work for me and kick into failsafe mode if AFR is not within the applicable window.
alfadriver mentioned:
I’d encourage individuals to get an information logging system, so that you’re not logging together with your eyes. Try to be driving.
And even on a dyno, a logging system will present you exactly the place the problems are as an alternative of making an attempt to juggle a/f, engine velocity, and a few load measurement.
Agreed, an AFR gauge is at finest a heat fuzzy, it is probably not helpful by itself. AFR knowledge logged together with RPM, manifold strain, and so forth is what you want for tuning.
So far as “failsafe” goes, IME widebands are significantly much less dependable than issues like gas pumps and injectors. I favor tuning the automobile with the wideband (on the dyno) after which turning off the automated provisions in order that the pc is utilizing the tuned, known-good gas map. It will probably monitor the AFR and activate an enormous pink warning mild if it thinks issues are going askew, however it mustn’t silently “repair” the gas combination.
In reply to codrus (Discussion board Supporter) :
It will be very nice if MS had an on board provision for a Bosch sensor. Then I’d belief it extra.
I take difficulty with the assertion, “the stoichiometric ratio, which is the perfect combination of air and gas that, when combustion happens, leads to no leftover gas or its catalyst (oxygen, on this case).”
It ought to learn : In a good combustion occasion, the stoichiometric ratio, which is the perfect combination of air and gas that, when combustion happens, leads to no leftover gas or its catalyst (oxygen, on this case).
An ideal combustion occasion isn’t obtainable. Take a look at a combustion occasion as a singles mixer with 100 males and 100 females. As an instance the mixer is 95% profitable; leaving 5 males and 5 females unpaired. If you wish to see all of the females paired, you have to introduce extra males to the mixer till that occurs.
Similar thought with gas/air mixtures. If you need max energy, you wish to use all of the oxygen within the cylinder (leaving unburned gas). If you need economic system, you wish to burn all of the gas (leaving unused oxygen). Richer than max energy mixtures present cooling; working to stop extra warmth, detonation and/or preignition.
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