Minimum Boost on an EFR 6258?
 

What's the minimum boost on an EFR 6258. I bought the low boost canister, but I'm starting to think I should have adapted something from another application. I want to tune at low boost first. Anybody have a good idea what the low boost canister will peak out at on a 1.8, with minimal preload?

Why not just leave the wastegate flapper open?

I figured step 1: tune with new bigger injectors and stuff for the non boosted regions with no boost (flapper open or equivalent). Step 2: tune with boost, but lower pressure to get a handle on what will happen with less risk to the engine. Step 3: tune with full boost.

Correct, as to why leave the flapper open.

So anyway, anybody know what I can expect for peak boost from an EFR 6258 on the low boost actuator?

you'll get whatever its rated for

6 psi cracking pressure, 14 psi wide open, maximum recommended operating pressure of 13 psi. Match-bot says a 28 mm wastegate is required to maintain 9 psi. The EFR 6258 has a 31mm wastegate, which implies it needs to be pretty far open to maintain 9 psi. Of course the Match-bot also says the wastegate needs to be open at 2500 rpm to prevent exceeding 8 psi.

Explain:
Your goal, in a clear logical way

Why someone would buy an EFR to run minimum boost is just odd.

I'm pretty sure the sites that sells the canister sizes have the info right there ( from what I remeber)

With the low boost canister you will be able to run around 8 psi. Note that your spool will be a tad worse set like that, since the wastgate will be almost open at 0 psi.

This is how I ran mine at first, then was set at 10 psi for most of its life.

I've already explained most of my goal. The piece you may be missing is that I want the fastest possible response from the turbo for autocross. It would be nice if they made a smaller EFR aimed at lower boost pressures, but as it stands, it seems to still be the most responsive turbo out there that doesn't fall flat on its face at higher rpm.

Sites that sell the canisters and of course Borg Warner themselves publish info. I've noted that info in an earlier post in this thread. It isn't enough by itself to answer my question.

This is what I was looking for, thanks! Interesting that you had the wastegate opening early when the specs say it cracks at 6 psi with 3 turns of preload on the rod. I plan to use the boost control solenoid to fix that anyway, but anybody else experience this?

Install the low boost can with minimum preload (though still tight enough to not get blown open at small pressures) and an ebc.

That's been the plan for months :D I started this thread because I was starting to get worried with the match-bot saying I needed 90% of the wategate size at high rpm that I'd be getting 14 psi on just the wategate or something.

Not that it will be the exact same on my setup, but do you remember how many turns it took to get to 10 psi?

Honestly I have no idea. It was quite a while ago, I had one of the very first turbos in the batch before the manufacturing defects were found. I just did a turn at a time until I was happy. I did go up to 13 psi accidentally once though, that was fun.

The actuator I got from south east power systems, that is a 2 port actuator with a 7ish psi spring I've got it with 2 turns of preload (1/4-20 thread) and its doing about 6-7, haven't been over 6k rpm though. Its running straight wastegate right now. If you call them, Mike will know what you're taking about if you ask for the 2 port efr actuator. You will need to come up with an extension for the rod since its short by about an 1-1.5" You can either turn one on the lathe or get a 1/4-20 (maybe its 1/4-28) threaded rod coupler and a short piece of rod.

That sounds like a good option. Since it sounds like I'll be able to make the low boost actuator work, I think I'll stick with that. Once I've got the EBC up and running the actuator makes a lot less difference.

At the risk of violent retribution I'm going to bump this. I'd like to hear how OP made out with the low boost actuator and EBC.

I'm guessing there's a bent rod or two. My own rod is standing erect at the prospect of carnage pictures.

Sorry to disappoint; all is well. Also, this turbo is presently in my MR2 Spyder, not my (sold) Miata. But 10:1 compression cast pistons and rods VVT-i 1.8 with EFR, so I'll keep going.

With the wastegate wired open, it made 3 psi by 7k.

The rest from clear memory of trends, foggy memory of exact numbers:


With the wastegate on and nearly no preload, terrible boost response (cracking pressure around 3 psi, 5-9 psi peak (never figured out why it varied, seemingly randomly, definitely higher when it was cold out but also some random variation. Actuator rod was coaxial, no kinks in vacuum line, etc).

With the wastegate cranked up a bit, 4-6 psi cracking pressure, 8-9 psi peak boost, 6 psi or so through most of the rev range. Much better boost response, but spikes with on off throttle at higher rpm (EMU as boost controller).

Wastegate cranked up just a teeny tiny bit more, spikes to 12 psi when IAT was very low. Seemed like the wastegate was sticking or something. Never found the issue. Might have been related to using an EMU as a boost controller.

Turned wategate back down, ran MBC. Not even remotely satisfied.

Bought turbosmart eboost street. Not impressed. Was under the impression it was a closed loop controller with rpm compensation when I bought it. It has a lot of features, but almost none of them actually did anything useful.

I say did, because I fit right in around here.... :D

I took the shift light output and ran it into a relay. I used the relay to trigger the external map switch on the EBC. I setup the first map as an up to 3500 rpm map, with gate pressure of 7.8 psi. It switched to a little lower duty cycle and a 3.4 psi gate pressure after 3500 rpm. This works great for 2nd and 3rd at autocross, and occasionally hammers the overboost protection in higher gears or up steep hills (if I go WOT between 3k and 3500 or so). When it falls back to wastegate only, it never drops below 6 psi or so, so for now I'm living with it.

Conclusions: running the low boost can from borg-warner and no boost control is not a smart move. You could have the same boost response out of a T25 from a wrecking yard. I have yet to run proper EBC, but what I have is still worth the money over previous Garrett options I've run. I'm running a full 3" with a cat and a Borla muffler. At 1500 RPM in 5th, it will build 2 psi by 1600 rpm. Under high load it makes full boost before 2400 rpm. Responsiveness is good enough so I don't want more by about 3800 rpm, and good enough so you'd be hard pressed to tell it from a bigger displacement engine by power delivery alone by 3k. I still have VVT-i and throttle transient tuning to do that should both really help spool, but it is already better spooling than a Gt2560 on an 01 VVT miata, so it isn't a high priority.