Legend Posted June 17, 2008 Share Posted June 17, 2008 I have tuned peak boost to around ~18.2 (3400-3800rpm) for 3rd gear. Boost tapers quickly after 4500rpm to 10.5 at 6500rpm. I live in Denver (5300ft, 12.1 atm), so between 3000rpm and 4500rpm my corresponding VF40 pressure ratio is between 2.4-2.5 (1.9 at 6500rpm). Is that too high of a pressure ratio for the VF40? That's roughly equivalent to almost 22psi at sea level(!) I might do a little experimenting. I'm thinking that b/w 3000-4500rpm I might do a series of 5 third gear runs on the same day with my current 18psi peak, then 17psi, then 16psi, then 15psi, then 14psi. I'll time each run from 2500rpm to 6000rpm and plot MAF/boost curves. I'll drop my boost curve to the lowest one I can without sacrificing power. Thoughts? My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
mwiener2 Posted June 17, 2008 Share Posted June 17, 2008 keep it around 15 psi. you'll lose some TQ on the low end, but pick up alot of HP higher up due to heat savings My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
LittleBlueGT Posted June 18, 2008 Share Posted June 18, 2008 keep it around 15 psi. you'll lose some TQ on the low end, but pick up alot of HP higher up due to heat savings WHAT? You are saying that the built up heat from low rpm will affect top-end power that much. 15 psi on a VF40 at altitude, at high rpm, is that also what you are saying? Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
rc0032 Posted June 18, 2008 Share Posted June 18, 2008 I love it when people add value. Link to comment Share on other sites More sharing options...
mwiener2 Posted June 18, 2008 Share Posted June 18, 2008 i meant peak target here's about the most you can get out of VF40 at 5500 feet http://i13.photobucket.com/albums/a257/mwiener2/scan0001.jpg http://i13.photobucket.com/albums/a257/mwiener2/scan0002.jpg My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
Infamous1 Posted June 18, 2008 Share Posted June 18, 2008 I lost about 1.5psi after my deletes, after I brought it backup I lost 1.5-2 degrees of timing yet my power stayed the same. However on my 100oct map with more boost it had more of an effect and put me off the efficentcy island as showed in my times. My current plan is to run peak boost until about 3800rpms then taper off vs runnng peak until 4800 like before. I think you definately should dial back and run comparable boost to an LGT at sea level running about 17.5-18psi, so around 15-15.5 would be about right. Link to comment Share on other sites More sharing options...
LittleBlueGT Posted June 18, 2008 Share Posted June 18, 2008 i meant peak target So how does 15 psi peak target affect top-end? Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
mwiener2 Posted June 18, 2008 Share Posted June 18, 2008 becasue if you try and do 18psi at this altitude, it's a flamethrower and heatsoaks the IC. 15 psi isn't anywhere near as hot and leaves the IC cooler, allowing the charge be cooled further as you go up the rpm band. start cooler, end cooler My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
Legend Posted June 18, 2008 Author Share Posted June 18, 2008 keep it around 15 psi. you'll lose some TQ on the low end, but pick up alot of HP higher up due to heat savings I don't know if I'd have to lose any TQ on the low end, actually. Why would I if I keep an aggressive spool and hit my new peak (15.8) around 2900 in 3rd gear? I think I'll go straight to a 15.5-15.8 (19.1 sea level equivalent) peak boost curve. I plotted my most recent 3rd gear pull (82F, 12.1 atm/5300ft) and another curve that I think might make more sense. Time for me to play with Mickey's road dyno... This would take my peak PR from around 2.5 to around 2.3. That's a pretty big difference. http://i28.tinypic.com/971jip.jpg My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
Legend Posted June 18, 2008 Author Share Posted June 18, 2008 Here is the PR I am currently running: http://i28.tinypic.com/szafyb.jpg And here is the sea-level equivalent boost curve: http://i25.tinypic.com/29lhgtf.jpg My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
LittleBlueGT Posted June 18, 2008 Share Posted June 18, 2008 Weiner: I know what you are saying, but I highly doubt it makes any difference, sounds stupid to give up low end torque because you think it will heatsoak the IC and affect high end hp, maybe on the dyno it would. Legend: You are on the right track, target plots seems pretty good. I would get the WGDCs figured out for the proposed target boost plot, then do back-to-back 3rd or even 4th gear runs (old target boost map vs new one) and see how much power you lost. If it is negligible you have your answer. Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
mwiener2 Posted June 19, 2008 Share Posted June 19, 2008 we see it on the dyno ALL the time and it does happen on the street, just nto as severe. Even with a GT35r, we can get the same numbers at 15psi as we do at 18psi. The difference is that at 18psi, timing is pulled at higher rpms due to the higher heat load. Middle rpm TQ fluctuates with boost. My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
LittleBlueGT Posted June 19, 2008 Share Posted June 19, 2008 we see it on the dyno ALL the time and it does happen on the street, just nto as severe. Even with a GT35r, we can get the same numbers at 15psi as we do at 18psi. The difference is that at 18psi, timing is pulled at higher rpms due to the higher heat load. Middle rpm TQ fluctuates with boost. Exactly, the dyno that has 100 mph air going through the IC. Quite saying half truths, I know what you mean, but you leave out a lot of info. And no, having higher peak torque does not mean you will lose top-end whp. Sure it might in some instances, but many times it doesn't. Full tune of 68HTA, KSTech 73 MAF, Racer X FMIC and ID1000s................by the DataLog Mafia!!! Link to comment Share on other sites More sharing options...
Infamous1 Posted June 20, 2008 Share Posted June 20, 2008 Did a bit of experimenting yesterday. I dropped boost from 18.5psi to 17.5 psi from 4-4.8K rpms and picked up 2.5 degrees of timing. Acceleration was about the same but with 105 degree IAT yesterday vs about 80 previously. Link to comment Share on other sites More sharing options...
rc0032 Posted June 20, 2008 Share Posted June 20, 2008 Did a bit of experimenting yesterday. I dropped boost from 18.5psi to 17.5 psi from 4-4.8K rpms and picked up 2.5 degrees of timing. Acceleration was about the same but with 105 degree IAT yesterday vs about 80 previously. Interesting...there are 3 components to tune (at a high level) boost, timing and AF...give on anyone one take on the other Link to comment Share on other sites More sharing options...
Infamous1 Posted June 20, 2008 Share Posted June 20, 2008 Yes, this proves that I was running a bit too much boost on the tiny vf40. All at the same 10.9 AFR, I was just suprised that I could add that much more timing back. This puts me at a pressure ratio of 2.21. Link to comment Share on other sites More sharing options...
Legend Posted June 20, 2008 Author Share Posted June 20, 2008 Hmmm... 2.21... I've done some experimenting and I was running too much boost too. I dropped by peak boost from 2.4-2.5 PR (17-18.2psi) from 3000-4500rpm to ~2.3 PR (around 16psi) and did not lose any power. I've done a couple iterations and am targeting a curve that holds a steady ~15-15.5psi (~2.26 PR for me) from 3000-4500 before tapering. I've also taken away 0.1-0.2 fuel (targeting around ~11.2 now) and added a half degree or so of timing. I've got a feeling I might end up quicker at peaking at 15psi than I was peaking at 18psi. My turbo will thank me anyways. My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
Infamous1 Posted June 20, 2008 Share Posted June 20, 2008 Before my pressure ratio was just 2.29 from 2800-4800 rpms, however I got an additional pressure drop from the removal of the TGV's. Link to comment Share on other sites More sharing options...
Deer Killer Posted June 23, 2008 Share Posted June 23, 2008 FWIW at sea level the butt dyno got severely disappointed anytime I exceeded 20psi, except for cruising on the highway in 5F weather. Timing was not pulled either. It's definitely done. Compared to my avo380 anytime I get a spike to 24-25 psi from a target of 21 I am simply amazed by the power increase, i.e. feel the front end lift and come back down at 80mph on the spike. Link to comment Share on other sites More sharing options...
Legend Posted June 24, 2008 Author Share Posted June 24, 2008 After several iterations I think I've found the ideal boost. My PR now hovers in the 2.2x's and peaks momentarily right at 2.3. That translates into 15.2-15.6psi peak from 3100-4000rpm at this elevation (5300ft). It translates to 19psi peak boost at sea level. Going from ~18.1 peak to ~15.5 peak did not cost me any power whatsoever. I was able to add back in a slight amount of timing and made it slightly leaner, but doing so didn't give me any additional power. I'm pretty confident my boost is in a much better place now up to 4500rpm, but I'm not sure if my boost could/should be higher after 4500rpm. Anybody else care to plot a 3rd gear run of rpm vs. PR for comparison? Oh, the pink line is my previous boost strategy and the blue line is where it is now. http://i30.tinypic.com/2ivxruf.jpg My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
mwiener2 Posted June 24, 2008 Share Posted June 24, 2008 So you settled on about 15psi..... My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
Infamous1 Posted June 24, 2008 Share Posted June 24, 2008 So you settled on about 15psi..... That is about where I thought would be best as well. Link to comment Share on other sites More sharing options...
Legend Posted June 24, 2008 Author Share Posted June 24, 2008 So you settled on about 15psi..... Yep. I wish someone would have just told me... My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
praedet Posted June 25, 2008 Share Posted June 25, 2008 Well, that is what I run Link to comment Share on other sites More sharing options...
mwiener2 Posted June 26, 2008 Share Posted June 26, 2008 fixed some boost leaks. Changed around soem hoses. Put a new pill in. now i'm peaking at 19psi and tapering to 15 at redline. My Mods List (Updated 8/22/17) 2005 Outback FMT Running on Electrons Link to comment Share on other sites More sharing options...
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