The past few datalogs I've been doing have been showing me hitting around 258% load by 4000rpm on my '03 VIII. Now what's bothering me a bit is I still haven't gotten around to swapping on my 10.5 hotside and o2 housing and I plan on tossing in a set of XS Engineering 272* cams in the near future. I'm still on stock injectors (which I'm pretty sure I'll need to upgrade in the near future although I have a walbro 255lph pump in for now) but since I'm nearing the end of my map's resolution (260% max) I'm getting a little concerned. Do most 8 owners tend to hit these loads on a stock turbo with just the basic pieces? It just seems a bit high to me and boost only spikes 22psi and settles to around 17-18psi through the redline. Any thoughts? I really don't look forward to rescaling my map lol.

 

Interesting... We have about the same mods with me having cams and a few little items and I'm nearing 260... I'm really surprised to see you at the same load with no cams and on an VIII turbo (Im on a IX)

I run much more boost also...

 

I know, it's kinda strange. I did my logs in 4th gear though so I'm sure that has some bearing on it being a bit high, but I'm wondering what would happen if say for instance I installed all the rest of the parts and the cams and ended up in the 280% range or higher? Would the map hit it's max of 260% and hold those values through the rest of the range? Obviously I'd want to rescale it to keep the resolution on the upper load portion, but I've also been under a bit of an impression that load % and boost pressure tend to correlate to each other.

 

I hit 260 load with 22.5psi before cams. Basically a TBE, O2 Housing and filter. Also, Load is derived from MAF readings and it its not 100% accurately scaled in your peak load area, it can vary your readings.

 

I hit 300+ around 4000rpm with BR TBE, 24 psi and stock everything else. My LC-1 wideband shows 11.3-11.5 at this point so no injector or fuel pump issues yet. This is not 2 byte load but calculated load since 2 byte would never show after modding the xml. I've hit 300+ repeatedly and had to raise my max load settings to prevent boost cut. No knock at these loads on 91 octane. I'm at 4000 ft elevation if it makes a difference. Boost is logged with JDM Map sensor.

 

Yeah, 300+ is way off there. If it isn't 2byte load, its not all that accurate. Also, tuning your cels from calculated load means you probably aren't even tuning the correct cell which needs adjustment.

 

Is this 2 byte load or calc load? In either case you can rescale the load cells if it goes beyond 260 and you want full control.

 

Recheck your boost gauge or whatever you're using. With your mods 260 load is around 24-26 psi I think.

 

Without 2 byte, I hit a max of around 355 while logging

 

easy fix, just rescale your load. Your calc load and 2-byte aint going to more than 30 off anyways, so thats like 2 cells over max. so if you hitting 300 calc load, could be your actually at 275. just rescale and problems solved.

 

Well I run the zeitronix boost sensor which is accurate to 0.1psi and I hit 22.5psi and 260 load. Load doesn't correspond with boost levels 100% accurately, thats just a ballpark figure. Anything that increases the engines VE will increase your peak load.

 

258 kPa absolute pressure - 101 kPa (atmosphere) = 157 kPa gauge pressure = 22.7psi

Looks like your load is spot on to me. What kind of boost gauge do you have? The MAF is probably more accurate than your gauge or map sensor for measuring load as it takes into account air density.

The load axis is scaled for kPa absolute pressure (300kPa is ~3bar absolute). Think of the MAF sensor as a 3 bar map sensor, except it reads air mass where a map sensor only reads pressure.

Changes to the VE of the motor will change the accuracy of these values unless everything is scaled perfectly. I'm still stock intake my 2byte load is upper mid 260's which equates to ~24psi when doing a kpa to psi conversion. which is about right as I'm hitting peak 25psi. It would not hurt for you to rescale to have some extra room but I think your ok as long as you dont plan on increasing the boost further.

 

Thanks guys, I appreciate the answers. Load is being logged via 2-byte, so I'm very confident that it's accurate. I don't plan on running more boost as it's pretty much a daily driven car and pretty fun (sometimes too much so for the street lol) as it is. Thanks for the breakdown of kPa vs. load%, that clears a lot of things up, especially with me being used to MAP based systems. After I get the rest of the parts on I'll do a quick datalog and see if the load's changed much, but I'll probably rescale at least 1 or 2 cells just to be on the safe side.