AllTorque Posted January 17, 2018 Share Posted January 17, 2018 23 minutes ago, Firetruck said: A lot of modern cars run stratified combustion, where they create a swirl of air/fuel in the centre of the chamber that is close to stoichiometry but out by the cylinder walls is nothing but air. Air, or EGR. 1 Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 17, 2018 Share Posted January 17, 2018 A combo of both I think. However with duel VVT some cars ditch the EGR and just run heaps of overlap to yeild the same result 2 Quote Link to comment Share on other sites More sharing options...
Roman Posted January 17, 2018 Share Posted January 17, 2018 Steatified injection is one of the wizard magic things of direct injection? Not sure if thats possibly to rerofit even if wanted to. What kind of cross hatch will i need on the bore to sute PLA pistons? 1 Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 17, 2018 Share Posted January 17, 2018 Yup definitely direct inject voodoo, however plenty of manufactures were still achieving it prior to DI. Toyota had lean burn 4AFE and 7AFE engines in the 80s. 1 Quote Link to comment Share on other sites More sharing options...
Roman Posted January 17, 2018 Share Posted January 17, 2018 Yes the lean burn 7afe was right till mid 90s i think? One of them used a combustion pressure sensor in the block which is cool. Butttt not stratified so much as a homogenous lean mixture... which is why they ditched it because emissions were awful. Unlike stratified which is more like a pocket of rich mixture and extra air around the perimiter that i dont think contributes to combustion/emissions in the same way. Tuning stratified injection with just a lambda sensor sounds like a ball ache! 1 Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 17, 2018 Share Posted January 17, 2018 Yeap it was the precursor to stratification, the swirl valves attempted to direct the fuel towards the centre of the chamber but it was far from matching DI. And as you say, plenty of NOx. Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 17, 2018 Share Posted January 17, 2018 I'd love to know how you'd tune it in an aftermarket situation. Sounds like a good way of blowing out the top of the pistons. 1 Quote Link to comment Share on other sites More sharing options...
ajg193 Posted January 17, 2018 Share Posted January 17, 2018 If you can pump in a mix of CO2 and N2 in place of actual exhaust gas for tuning purposes and then come up with an AFR offset function depending on how much "EGR" is being pumped in to adjust to the actual combustion AFR is then you might be alright. Quote Link to comment Share on other sites More sharing options...
Roman Posted January 17, 2018 Share Posted January 17, 2018 1 hour ago, Firetruck said: I'd love to know how you'd tune it in an aftermarket situation. Sounds like a good way of blowing out the top of the pistons. I think MAF is the answer - if you can quantify the amount of air coming in then you can quantify the fuel, even if its not a traditional ratio I guess. But yeah god knows how you'd tell anything from a wideband. Maybe EGT would earn its keep here. 2 Quote Link to comment Share on other sites More sharing options...
AllTorque Posted January 17, 2018 Share Posted January 17, 2018 Lexus and some new Toyotas switch between Otto and Atkinson cycle by keeping the intake valve open until the piston is half way up on the compression stroke. They use a air flow meter that measures air going in and out. The have electronic VVT hubs for wider range of movement. 2 Quote Link to comment Share on other sites More sharing options...
Roman Posted January 17, 2018 Share Posted January 17, 2018 Interesting! I've seen that electric VVTI on the 1UR (?) V8. Oh yeah so that leads me to another thought. People say that you can reduce pumping losses (and so improve economy) by reducing vaccum amount. But, you also have compression losses as well. If you have more vaccum, you have less air to compress when the piston comes back up. I wonder what the balance is here? Looking at BSFC maps it seems like you can very quickly move up a few isobars by staying away from that very low load area. But then very diminishing gains towards that 80%ish throttle peak. But also, by changing AFR or cam timing etc you are changing the shape of the BSFC map as you go. Hmm. Quote Link to comment Share on other sites More sharing options...
yoeddynz Posted January 18, 2018 Author Share Posted January 18, 2018 21 hours ago, Firetruck said: Yup definitely direct inject voodoo, however plenty of manufactures were still achieving it prior to DI. Toyota had lean burn 4AFE and 7AFE engines in the 80s. And without the need to have a full valve de-coke every 100,000km. I'd been reading recently about how choked up some DI engines are getting from lack of fuel cleansing. Quite amazing how bad some get. 1 Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 18, 2018 Share Posted January 18, 2018 Oh dude I deal with them first hand. They get fucked. 1 Quote Link to comment Share on other sites More sharing options...
yoeddynz Posted January 18, 2018 Author Share Posted January 18, 2018 I have a GDI Mitsi Legnum coming in tomorrow with what the owner suspects is a coil pack issue. Hmmmmmmm. Luckily he only needs the car a while longer and will then flick it off. I'm not even going to touch the inlet. Its common place in the UK to get your car de-coked now. They use little mirrors and dentist picks etc. How the fuck would one avoid shit dropping in ? I guess a decent vacuum and some luck? That carbon stuff doesnt compress well so it would only take a little bit to be sat on a valve and get squashed against a seat so destroying the seal? Apparently the later gen BMW minis are terrible with this. Ha- my dad would laugh. He used to have to do a regular de-coke on his Morris Minor. Come full circle (except without the leaks) Quote Link to comment Share on other sites More sharing options...
kws Posted January 18, 2018 Share Posted January 18, 2018 They can also use walnuts (?) to media blast the valves and inlet ports to clear the carbon. Quite common on VWs and BMWs. Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 18, 2018 Share Posted January 18, 2018 The Threebond intake cleaner is boss. I highly recommend it for DI engines. Quote Link to comment Share on other sites More sharing options...
Roman Posted January 18, 2018 Share Posted January 18, 2018 Yeah thats why some Toyota DI engines still have an injector in the port as well. Ive seen some gdi engines that blew my mind with how fucked they looked! Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 18, 2018 Share Posted January 18, 2018 The diesels are worse. I've cleared out a few 1KDs who had less than half the diameter of the intake remaining. The EGR cakes it full of carbon, and the cakes itself up with carbon, and the the whole system chokes itself. Customers have been blown away with how much power their Hilux makes when it leaves the shop 1 1 Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 18, 2018 Share Posted January 18, 2018 Lol I've Snapchatted a lot of the pics but haven't actually saved any as an example Quote Link to comment Share on other sites More sharing options...
Yowzer Posted January 18, 2018 Share Posted January 18, 2018 Nom nom This level of fucked is so common on 1KDs, and I'm sure many others. 1 1 1 Quote Link to comment Share on other sites More sharing options...
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