No its not valve overlap. Its just keeping the AFR where it belongs. Egt goes up as afr goes down, which is opposite of gas. To get enough air molecules into the motor to burn more fuel, you need higher air density. So you need higher pressure at similar temp, or lower temp at the same pressure, etc.
It only really matters at higher duty cycles, because the motor can tolerate really high egt for short amounts of time. But if you want to be safe, and you dont want to have to watch your egt like a hawk every time you cane it, you do the math and provide a cushion with some headroom to maintain a safe AFR for the motor even at max fuel. This is where most designs fall short, because it requires a huge turbo to do it right, which is tremendously laggy on a small displacement motor. It will idle, then take forever to spool, and then when it does spool the alda adds 2x more fuel at the same throttle position, which means it is undriveable for anything except burnouts. An example would be the hx40, which people use to good effect, but it is actually too small to give you enough air and clean exhaust at the fuel levels required for 450hp. Smokes like hell for a few seconds before spool, then goes like hell with high egt and still too much smoke. Not a very refined package. Going to an hx52 just makes the low rpm and spool characteristics worse, so it becomes undriveable. Compounds give you the early spool so the throttle can be used at all rpms to modulate the power - not just above 3000. Use a vnt or a small he221 or hx30 with a 6cm housing to get early spool, then use that air mass to spool the large turbo. The large turbo just pressurizes the room that the small turbo lives in, so that it can flow 2-3x more air mass than it was designed to. This gets back to the intercooler air flow resistance question. Yes 80 lb/min is a huge volume at 14.7 psi. But at 60psia it is a lot less volume and it flows just fine through the intercooler. Volume flow through the motor per revolution remains constant. The manifold air density varies by a factor of 3 or 4, depending upon how efficiently it is compressed and cooled and what ambient temps are. On Thu, Dec 27, 2018, 9:46 AM MG via Mercedes <mercedes@okiebenz.com wrote: > So increased overlap on the valves to blow > cooling air through? I guess I have to read > up on a lot of that stuff. It's been a long > time. I'm only running around 14 or so on a > stock 617 engine with 313,000 miles on it. > Thinking of possibly adding propane injection > but no good place to put a tank in a station > wagon. > > Karl Wittnebel via Mercedes wrote: > > Yes an egt probe is sort of a given with any added fuel. I may do a boost > > controller to the alda pressure to regulate how and when it adds fuel. > > > > With adequate intercooling, adding air (increasing AFR) cools the egt, so > > maintaining 17:1 or higher is the goal to prevent excessive smoke. It > would > > run a bit cooler at 18:1. > > > > > > On Thu, Dec 27, 2018, 6:43 AM MG via Mercedes <mercedes@okiebenz.com > wrote: > > > >> Make sure you have EGT. 45psi is way up there > >> beyond piston melting range. might need > >> water/methanol injection also. > >> > >> Karl Wittnebel via Mercedes wrote: > >>> Sent it from the wrong account so it bounced. > >>> > >>> Great feedback Mitch. It is really just a packaging issue and > maximizing > >>>> frontal area on the car. I cannot fit a decent air to air coooler up > >> there > >>>> due to the curve of the bumper fascia and the existing bumper. > >>>> > >>>> I will likely add another smaller water cooler in parallel in front of > >> the > >>>> right front wheel, from an M4 or M5. > >>>> > >>>> Only two differences I can think of from the Cruze. One is boost. I > will > >>>> be running up to 3 bar of boost, like 45 psi. That is a lot more heat > >> than > >>>> 19psi, assuming similar motor displacement and rpm. My setup will > >> require > >>>> up to 80lb/min at full trot, which I do not plan to explore very > often, > >> but > >>>> I keep thinking that going up the grapevine when it is 90 degrees out > >> with > >>>> kids and wife and a car full of luggage and the AC on might want a lot > >> of > >>>> intercooler. That is pretty much my worst case scenario in terms of > heat > >>>> dissipation, unless I take it out on a road course, which would be a > >> lot of > >>>> fun and is sort of my gold standard for performance. > >>>> > >>>> There are more variables to chase with air to water. Namely the water > >> flow > >>>> and the pressure/flow curve on the fluid pump. Most of the pumps used > >> are > >>>> low pressure, high flow. The heat exchangers become the bottleneck, > >> mostly > >>>> the radiator. So you need a good higher pressure pump like a Pierburg > >> 50 or > >>>> 100 series to make the required flow happen at 1 bar or whatever. I > >> think > >>>> some of the higher end mercs use them, and BMW also. This is only if > you > >>>> want it to keep up with the heat input at high sustained power output. > >>>> Otherwise, for short bursts of power, a big tank of water does the > trick > >>>> with a crappy pump. > >>>> > >>>> I plan to fully instrument the thing. Unfortunately I have to add the > >>>> whole setup to the car, as none of the required sensors are in place, > >> e.g. > >>>> TPS, IAT, ambient temp, pre/post intercooler water and air temps. And > >> the > >>>> turbo rpms to see where it is running on its map. I should be able to > >>>> calculate cooler and turbo compressor efficiencies for both turbos. > >>>> > >>>> Thanks again for the graph. Cool Cruze! (but no diesel? What kind of > >> motor > >>>> does it have?) > >>>> > >>>> > >>>> > >>>> On Wed, Dec 26, 2018, 4:04 AM Mitch Haley via Mercedes < > >>>> mercedes@okiebenz.com wrote: > >>>> > >>>>>> On December 25, 2018 at 7:55 PM Karl Wittnebel via Mercedes < > >>>>> mercedes@okiebenz.com> wrote: > >>>>>> Switching to air/water. Not stock. Maybe people have some input on > >> heat > >>>>>> exchangers... > >>>>>> > >>>>>> https://youtu.be/kjTc9UYTlFk > >>>>>> > >>>>> I find it hard to get excited about water/air. > >>>>> If I had a rear or mid engine car it might be necessary. > >>>>> > >>>>> Attached is a screenshot of a 8 second full throttle hillclimb in a > >> 195hp > >>>>> gasser at 19psi boost with a factory A-A intercooler smaller than the > >> one > >>>>> that came with the 1999 E300. > >>>>> Pic of cooler: > >> https://www.gmoutletparts.com/oem-parts/gm-cooler-39116550 > >>>>> I can measure the cooler if you want. > >>>>> > >>>>> Ambient temp was 30-32 degrees F, manifold temp actually dropped from > >> 43 > >>>>> to 39 during the run as the car accelerated to 70mph. Water temp > stayed > >>>>> pretty constant at 181-183. > >>>>> If manifold temps with that little A-A are about 10 degrees above > >>>>> ambient, I don't think you're going to beat that with W-A unless > you're > >>>>> towing heavy loads at low speed and have a lot of room up front for > >> coolers. > >>>>> With an unladen car, you simply can't keep your foot in it for long > >>>>> without airspeed reaching 'wow, look at that > >>>>> cooling'._______________________________________ > >>>>> http://www.okiebenz.com > >>>>> > >>>>> To search list archives http://www.okiebenz.com/archive/ > >>>>> > >>>>> To Unsubscribe or change delivery options go to: > >>>>> http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > >>>>> > >>>>> > >>> _______________________________________ > >>> http://www.okiebenz.com > >>> > >>> To search list archives http://www.okiebenz.com/archive/ > >>> > >>> To Unsubscribe or change delivery options go to: > >>> http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > >>> > >>> > >> _______________________________________ > >> http://www.okiebenz.com > >> > >> To search list archives http://www.okiebenz.com/archive/ > >> > >> To Unsubscribe or change delivery options go to: > >> http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > >> > >> > > _______________________________________ > > http://www.okiebenz.com > > > > To search list archives http://www.okiebenz.com/archive/ > > > > To Unsubscribe or change delivery options go to: > > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > > > > > > _______________________________________ > http://www.okiebenz.com > > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > > _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
