Out of Turbo
 

I finally have my car sorted a bit better and started messing with higher boost on E85. Running efr6258, kraken low mount. etc. etc.

5280' of elevation (Denver) (83KPA atmospheric pressure)

Pretty sure this thing is maxed out at about 24 psi / 250 KPA. I have my solenoid fully closed on the attached log/VD dyno.
--please ignore the AFR issues (still sorting fuel at these levels and I am a shit tuner - but it hasn't blown up yet )

I do have a high flow cat in the exhaust. Assuming going no cat would help quite a bit (I am running full 3" exhaust).

Does this seem reasonable to be maxing out this turbo at these levels? - I guess I assumed it would flow some more? Perhaps I need to do some oversized valves and remove the high flow cat to help flow? Or should i just pony up at upsize to a 6758 (any thoughts on actual increases without other engine/head work here?)

In search of some more power than this. Car is too slow....6 speed is still in one piece. Any thoughts/tips? I am assuming a lot of this is due to living at altitude and I screwed the pooch picking this turbo at this altitude.

https://cimg4.ibsrv.net/gimg/www.mia...a5a2dd1c33.jpg
https://cimg3.ibsrv.net/gimg/www.mia...981238157d.png

man I know altitude is a big factor, but I make that same power (touch more up top) with a 6758 at only 17psi... I do see your boost dipping in the high end -- with a spike down low which is usually a sign your wastegate isnt opening enough, which the preload on the BW turbos impacts greatly. I would try to get that sorted out and see what kind of boost you can hang on to up top.

Yep, that looks about right at 5280. Altitude is a bitch.

67mm compressor is next step, but you will be between 4700 and 5000 before hitting your manifold pressure target.

Stop using the term "boost" it confuses the crap out of people.

Ted - I just want everyone to run around as confused as me.:nuts:

Also - any chance you will be a Slush fest at PPIR at the end of the month? Would be nice to meet some fellow Miata guys down there. I will be doing the open lapping in the morning

I would say it is unlikely I will be there, we are in the heart of graduation season, looks like the neighbor girl has her thing on the 28th. I am sure there will be some of the other miata people there.

I will say that it is highly likely you are out of wastegate, and a stiffer spring should allow you to hold manifold pressure more effectively. You probably shouldn't expect significant power gains though.

not OUT of wastegate, but the way the preload works on the BW turbos is that by adding preload to increase boost, you effectively reduce the angle that the wastegate can open. We were having slight overboost issues when I was on the dyno and my tuner explained it and demonstrated it with the dyno. Basically moved the nuts to the very end of the threaded rod and got rid of the overshooting because it was now free to open the full range. Different than being out of wastegate, which would be highly unlikely with a BP and EFR. The move would be a stiffer spring with the preload set all the way to the minumum

I ended up switching my medium boost canister to the high boost canister, which gives me about 16-17psi and no boost overshooting

Dr Sep, Dude, not to be a jerk, but you are out of your lane here.

Admittedly, I haven't dealt with the altitude you're in and I'm not all that familiar with BW's wastegate setup... but I'm just having a hard time buying that a 6258 is tapped out at 290whp on E85. What does your timing map look like? I've seen huge gains up top with timing advance at higher rpms, and more aggressive timing typically helps hold boost a better too.

Ted mentioned a stiffer wastegate spring, that's certainly worth a try if it leaking. If you can reclaim that ~6psi drop you're losing there's certainly some power to gain there.

Sep. I do not believe this an overboost/too little wastegate opening issue. I am targeting 250kpa (actually trying to get more out of it - was hoping for 280 kpa). The wastegate is 100% closed (unless it is being forced open a bit due to too weak of a spring) It is not "over boosting then dropping to desired levels" like you see with too little wastegate opening. It is hitting a maximum level of 250KPA then dropping because the turbo is maxed out, To hold 250KPA at any RPM above 4681 in those logs the turbo needs to move more air (as the motor spins faster it takes increased air volume to maintain similar pressure) - which it can not do. This is shown when you tune an EBC boost duty table - typically you see something like 5% more duty cycle as your RPM increases to sustain a "flat line" boost curve as RPM increases - faster the motor spins, the more air volume is required to maintain the same KPA at the manifold. If the turbo is producing its maximum possible air volume/pressure (250kpa) at 4681 rpm, and it continues to provide that same air volume at 7000 rpm your manifold pressure drops.

At least that is my understanding of it.

Ted - so you think there is a chance the WG is actually being overpowered a bit and leaking? I may go with a high boost canister and see if that helps squeak a few more kpa out of it.

Do you guys think deleting my cat would help this problem at all? I am sure less backpressure = quicker spool, but am interested if it would also help overall compressor speeds/max pressures?

pdexta - sadly I do not have my tune here at work, but if I remember right timing table is around 16-20 degree range at 250kpa. Once I get some time I need to get on a dyno and actually build a legit timing table to squeeze some more power out of it.

Yes I hypothesize with a high degree of confidence that your wastegate is unable to withstand the force required to generate more than about 275 whp with that compressor. Keep in mind that your PR across the compressor when you actually hit 250kpa is almost certainly well in excess of 3. Your hotside is going to have major back pressure and cost you hp. Having worked with a couple/few 6258s in this area, I have yet to see one crack 300 whp (uncorrected), and it seems everybody wants all-of-it, so attempts have been made.

Edit: oh and yes your cat is robbing power, quite a bit actually.

Ted - that is what I assumed. Looking at the compressor map a bit more in depth last night it looks like I am starting to move into the less efficient ranges of the turbo as I search for more power.

Appreciate all the insight and knowledge.

Perhaps I need to just enjoy the car like this for a while, I am severely addicted to the power search, my wife thinks I have a problem.

Ted I do try to stay in my lane thanks! Didn't realize he was EBC, was literally just offering my real world experince. Sad I got a neg cat for that. No disrespect towards you either, was just trying to rule out simple things. Sir, King, what-have-you.

Carry on, good luck on your search for power -- *homer simpsons into the bushes*

lol at the ninja neg-cats. sigh, my faith in the future is degrading.

Here is a thread you might find enlightening

I was on the dyno and my tuner explained it and demonstrated it with the dyno. Basically moved the nuts to the very end of the threaded rod and got rid of the overshooting because it was now free to open the full range.
Speed Test