1st Dyno run on VT High Load map - wtf?

[maestro]

So I had my first dyno run today - somethign's clearly not right. Anyone got any ideas? Unfortunately I wasn't allowed to log the runs on my laptop because I wasn't allowed near the dyno for "H&S BS".

This isn't healthy though - the car's clearly ramping up the boost nice and quick then backing off for some reason and never ecovering from there



So how do I go about troubleshooting this mess?

[Steve @ VersaTune]

It looks like a boost spike. The ECU appears to have over reacted and dropped boost then it recovered. Modify BCS DC Base , BCS DC Load Target Correction, and Accel/Decel Req Load Modifier tables and street test to get a smooth boost curve. Free flow intake and exhaust alter the spool profile of the turbo. You need to tune that spike out and reduce the load target correction so it doesn't over correct. Take some General Performance preset logs of spool up in 4th and post them here. Do you have an aftermarket BCS like a Grimmspeed?

[maestro]

Yeah, I have everything you mention

I'm running a Corksport SRI/TIP so that's your free flow intake. I've got a custom decat so there's your free flowing exhaust. I've also got a Grimmspeed EBCS (albeit in 2 port mode) so that's that covered.

To be honest, all your advice just went straight over my head since I haven't started tuning yet - I've merely done my calibrations and whatnot. What I wanted was a nice baseline dyno graph to refer to but all I got was this for Christmas.

[skiptownmcat]

Get that ebcs plummed in 3port mode!! In the meantime reduce BCS base by 5 in the area of the spike. Log a street wot run and keep reducing until the spike is nearly gone.

[maestro]

Yeah I think that's gotta be the way to go. I'll plumb it in 3pt mode and install the 3pt map from the database.

I guess what I don't understand is why the ECU thinks that's a boost spike I mean it's not like it's anywhere near 20psi or anything. What is it that makes the ECU think "noooo!" when the boost ramps up? I want fast, hard boost - surely?

[skiptownmcat]

Yeah I think that's gotta be the way to go. I'll plumb it in 3pt mode and install the 3pt map from the database.

I guess what I don't understand is why the ECU thinks that's a boost spike I mean it's not like it's anywhere near 20psi or anything. What is it that makes the ECU think "noooo!" when the boost ramps up? I want fast, hard boost - surely?

If you have too much wgdc the boost is starting way above what is required to hit your load target. Coupled with some free flowing mods making the problem worse, the ecu freaks out and cuts boost to self preserve. At least that's my understanding, steve will probably correct me though

[maestro]

So does that not mean that one solution is just to increase the requested load target thingimabob?

[skiptownmcat]

So does that not mean that one solution is just to increase the requested load target thingimabob?

I would go with the safer option of removing the spike first, post up your tune and I'll take a look if you want.

[maestro]

It's just the standard high load tune The only thing I've altered is the MAF calibration thingimabob and I leaned out the normal target afr thingy to 11.8 from 10.8 'cause 10.8 is piss wet rich.

[mituc]

That spike around 3000rpm is present even with the stock tune. Now, when using flow mods (especially better flowing exhaust) that spike is even bigger if it's not addressed with a tune. This is what happened in your case.

11.8AFR is way too lean. Theoretically you're getting closer to the best AFR performance wise (around 12), but for our engines 11.8 is too lean and dangerous.