Begi s4 overboost > looking for advice.
 

I am having a hard time figuring out how to troubleshoot an overbooting issue and seek the advice of the community. This subject has been beaten to death but it seems most people get a port and call it a day or go to an external gate. My turbo is already ported and I’d like to avoid going external if possible.

First my car:
01 vvt
Begi S4 kit
Begi separated gases downpipe that flows back into the exhaust
3” exhaust from Abe with a cat and resonator.
Garrett gt2860rs .64ar
Wastegate has already been ported by Begi according to Begi themselves.

I wired the wastegate open and did a 3rd gear pull. The car made 2psi up until ~5k where it creeps to 12+psi verified on boost gauge, megasquirt log, and butt dyno in 3rd gear. With a 7psi actuator with the proper 3 turns of preload the car makes ~15psi. I assume this means either the port isnt capable of pushing out enough exhaust gas or the wastegate’s pipe isnt free flowing enough. Is that accurate? What could other culprits be if any? Attached are 2x pics of how much the flapper opens.

I have seen a few threads on here where people grinded out the exhaust housing entering the wastegate to allow for smoother flow for the exhaust to exit the wastegate. Is that something that is worth looking into? I already have the turbo yanked out of the car at the moment and I plan to take it somewhere to see if they can port the turbo more than it already is if that is a viable option. But short of going to an external setup I am not sure what is worth trying.

How about wiring the WG open and check how much boost this nets you? That should be pretty definitive.

:party:

OP, the best you can do is port the hell out of the wastegate, but you may never be able to run 7psi on that setup. You have the worst possible combination of parts for low boost. Tubular manifold + small A/R Garrett turbine + decent downpipe + big exhaust = boost creep city.

I would seriously consider a swap to an EFR setup before investing the money in an EWG mainfold/downpipe for that turbo. The EFRs have none of these issues, owing to far better wastegate design.

this is very important and likely your only non-expensive option.

the path to the wg port is just as important as the port diameter itself.

you can easily do it yourself with a grinder and carbide burr btw.

Install an exhaust restrictor.

dont' make me ban you

:hatecat:

:giggle:

Some threads to reference from

https://www.miataturbo.net/diy-turbo...exhaust-80152/

https://www.miataturbo.net/general-m...aterial-80058/

Thanks everyone. You guys pretty much confirmed what I thought. I will likely try to grind the housing and if that helps at all. Maybe check to see if any more of the wastegate port itself can be opened up. If that doesn't get me where I want to be I will look into other options. I will post an update on how it goes.

Just took off the manifold to see what I'm dealing with while I hunt down a carbide burr. Figured I'd give an update before the update. This is my starting point. Going to widen the channel and smooth some of the sharp edges.

https://www.miataturbo.net/attachmen...ine=1460238715

https://www.miataturbo.net/attachmen...ine=1460238715

Im going to go ahead and ask this question again but.. Do you really need it to not creep up top?

do you have insufficient injectors?

Dann

Either grind the entrance slope to the WG, let it run 12+psi, or switch to a .86 turbine housing.

did we do this yet?

If I didnt have stock rods this wouldnt be an issue. The car creeps to 15-16 psi in 3rd gear and it will get worse in 4th, 5th, and 6th. The end goal assuming I stay with this turbo setup is to run 10-12psi wategate with an MBC set to 12-14psi and not nuke the car at an autocross.

With the wastegate wired opened the car peaked at 12.7psi. With the 7psi actuator hooked up it made 15.x both in 3rd gear (same day/air temp/road). Does it stand to reason that with the actuator opened I should only be seeing 12.7psi? I was previously thinking with the actuator attached there is more exhaust gas trying to escape at once when the flapper opens compared to having it wired opened and it venting the entire time. But really, I could just be way off base.

Would the larger .86 A/R housing fix my problem? Large wategate? I need to read some more about how badly that would hurt spool. I am not a track rat so it might not be a big deal.

It sounds like my options in no particular order are:

1. Pray to turbo kitten for unlikely great porting success
2. EFR
3. External WG
4. Larger housing
5. Build motor

Another option is an ewg manifold with a tial 38mm

I have decided against modifying my current turbine housing any further. Its ported to a point where I don't think any smoothing I do will have a significant impact. That coupled with a few cracks forming I think its best to replace it. I am going to hunt down a .86 a/r housing.

One thing I just discovered was the wastegate baffle. I assumed it was a standard piece but it is actually welded in place and not from Garrett. If I get a new housing is that something I am going to want to make sure is on the new housing? Could that be reducing the flow to the wastegate being another culprit to my boost creep?

This is the piece I am referring to:
BEGi

you should be able to get it to stay at 13psi with the actuator attached. remove some preload.

Sooooo...

When are you doing this? :eggplant:

First off I am an moron because that baffle is on the other side of the housing. That can't be an issue.

I played with preload (even taking it down to no preload) prior to pulling the turbo with basically the same results. :dunno:

the arm must not be able to open it as far.

Basically. Even at max travel, the actuator is going to slightly restrict flow through the orifice. Remove it and flow will increase slightly.

Sounds like I am screwed with the hardware I have. Would a large turbine housing be a solution? If I shouldn't waste my time I guess I will go right to EWG like everyone else seems to do.

Thanks again for everyones input on this!

I used an exhaust flange as a spacer because the arm wasn't able to swing all the way open. It's not preferred but until I redo my setup it works. I don't have any creep with a very similar setup.

Downside is it leaves very little room between my dp and my rear shelf and core lines.

My feeble brain can not possibly comprehend though how it makes any sense for the waste gate to open into the exhaust port. I mean the arm opens (not fully) and when it does open it opens into and plugs 3/4 of the exhaust port on my dp... anyway I digress. Maybe I should go read Maximum boost for an explanation.

This may not be your issue but it was mine. Before i motor swapped to 1.8 my 1.6 had an S style down pipe and I didn't have any creep issues like the separated dp.

If you look between my dp & turbo you can see the silver piece, the extra exhaust flange i use as a spacer

https://www.miataturbo.net/attachmen...ine=1460408253

Try hooking up the wastegate to some pressur and see if you're able to make the WG swing open at a certain PSI... see if you hear it hit metal on metal from the inside :dunno:

I'd try that before changing everything else out... Krisset makes a good point using a flange as a spacer. That'd be cheaper as long as the studs are long enough.

Have you tried wiring the gate open with it unhooked from the wastegate? See what psi you put out with it wide open :dunno:

Have you called and talked to Corky@Begi yet about this?

If you're considering EWGs, ATP sells a 2860 turbine housing with a v-band port. This is what FM uses in their FM2R setup, it lets you use the manifold you already have, although you'll need to modify the downpipe if you don't want it to dump to atmosphere.

https://www.miataturbo.net/attachmen...ine=1460409018

(edit: I don't actually know where the turbo flange is on the BEGI S4 manifold, so you'd need to check there's enough clearance to use this.)

--Ian

Theres not. But the suggestion to check and see if flapper may be binding is valid imo

Send a dyno of it doing this or a datalog on the street.

As someone who runs 18-20 psi into stock engines all the fucking time with not a single failure id be happy to look at it and tell you if its a legitimate issue or not.

Dann

This /thread problem solved.

Just tack weld the iwg arm or make up a quick bracket or buy one they are cheap and super common.

Except I can almost guarantee that that housing will not work on his manifold. I believe the wastegate will run into the shock column.

:laugh:

I have been in touch with Stephanie at begi. She has been extremely helpful actually and offered to send me a 1/8" spacer and longer downpipe studs earlier today to try. With the downpipe bolted on the flapper does hit the downpipe but it opens to the angle in the picture in my original post. I assumed that was enough for proper flow but a spacer is worth a try if it lifts the flapper even more. If that can fix it I can just have it welded on. I can hit it with an air compressor tomorrow and double check if the gate is getting hung up.

That housing would be ideal but like others have mentioned theres no way that would fit.

The car dyno'd at 250/230 at 14psi on a dynojet. Crappy picture of dyno is in my "build" thread 1st post found here https://www.miataturbo.net/build-thr...-slayer-81107/

Actually if you look at the dyno where its likely creeping the most the power dies out. I wonder if the timing is too low (I don't have a log of that dyno pull). I will have to put a few runs in VD to see if is doing that constantly. That might be an entirely separate issue though?

IME 250 on a dynojet isn't likely to break rods. My motor did around that for 40K miles before I lost it to a throttle body screw failure.

--Ian

If I can get it to stay at 14psi although still not ideal I don't think I would touch it.

Did a 5th gear pull and hit 18.9psi :eek:. Boost reading in VD is wrong..not sure why. At any rate this is why I fear for my motor. Need to turn on overboost protection on and never do that again.

This was never an issue in the warmer months. I think the whole time I have owned the car its only been on the road win 75+ degree temps. All of these issues are in sub 65 degree weather. Maybe the best solution is to not drive it in cold/mild weather.

https://www.miataturbo.net/attachmen...ine=1460422760

The new game plan is to check the flapper for hang ups again, test actuator again with air compressor, try a spacer in that order. I will post the results when completed.


Side note: 5th gear in a miata is either terrifying or I am a grandma.

I'm having the same issue with my 2560 on fm manifold and straight through exhaust back to a Honda boy fart can. That atp ewg housing won't fit a 2560r. Smallest it will fit is a gt2860rs. I've been talking with jeremy at fm for solutions. Called begi this morning and am awaiting a call from Stephanie to discuss effectiveness of IWG porting

I can only speak to my setup but the issue isn't that flapper opening all the way. It's that when it does "open" it really isn't opening. It pivots and ends up inside the exhaust port. It basically plugs the hole it's trying to exhaust to.

On my dp there is also a little flap that segregates the wastegate from the regular exhaust. So basically before I added the spacer the wastegate would open at pressure into and mostly plug the port. The partition of course prevents any kind of relief as well. Anyway anyone with half a brain can explain to you how useless this is. may as well weld it shut and just do what dan does and run 18-20psi on stock internals.. #ALLOFIT

https://www.miataturbo.net/attachmen...ine=1460655531

If you look at absurd flow or artech stuff it doesn't seem like they do anything a lot different on that flange though. They don't put that little divider in either so maybe if the wastegate is hitting on those downpipes it isn't nearly as noticable since the excess gas can escape/bleed over to the normal exhaust? I don't know... I don't have any experience with those setups but just thinking out loud.

I never understood why they don't just make a bellmouth like just about every other company ever.

the claimed flow disturbance is literally just a stupid theory that has been tested to not affect power any more than maybe 1hp, and you would never run into any of these interference or obstruction issues.

Is the fm cast piece more of a bellmouth style? I'm just trying to get an idea if the IWG porting service by begi will stop my boost creep. Obviously there is only 1 way to actually find out but I'd like some insight. (2.5" dp to 3inch straight pipe to straight through muffler 2560r)

theirs is a cast "bellmouth" on the outside but separated on the inside. I haven't really heard of too many issues with those having interference, the ports inside are much larger than the begi SGDP

your 2560 is likely unported which would explain the creep.

this, or at least design it better so the flapper itself doesnt block the flow path.

I'm pretty sure if you remove that extra divdier they added, you'll be able to control boost better since diverted gas can just flow through the main tube as well...

I agree. If you google image downpipe you'll end up staring at a ton of diesel and subaru dps but a vast majority of them collect into one big collector.

I'm kind of fair weather when it comes to my miata cause it's just a project but maybe some day i'll update my build thread and throw some logs in there. I understand the benefits of an EWG but since i put that spacer in my IWG has been rock solid.

The efr lineup is regarded as having a good internal wastegate right? I have been in and out the last year so unless the consensus has changed perhaps take a look at that turbo. The reason it has that long profile is in part because of how the wastegate operates. It opens inside the turbo body and flows with the exhaust unlike the gt series that needs a little porting help. At least that's my take/analysis on it at first glance.


https://www.miataturbo.net/attachmen...ine=1460659750

Yeah, the efr hotside is well designed, most here will agree that it's definitely the IWG to have.

many modern OEM"s use that design too on their non-EFR turbos

most (all?) never have creep issues

When I put my spacer In I also took my grinder to that divider. Maybe overkill but I have no creep.

yeah the idea of the divider and divided pipe is sound, but if you cant actually flow the exhaust out the tube, then like it's hurting not helping.

Accurate first glance, sir. EFR6258, full 3" exhaust (turbo to tailpipe), low-boost actuator, minimum preload:

https://www.miataturbo.net/prefabbed...2/#post1272746

If you don't speak datalog, this is a 2-3-4 pull showing 141kpa (6psi) at redline. Zero creep. EFR IWG FTW.

Attachment 231985

Yep. And once I added the spacer in I just made the divider useless anyway. No reason to not give it more room to flow together instead of leaving that divider and creating a weird pocket.

the subabroz actually did a test between the two designs.
using two units that are designed well enough to not creep
the difference was about as much as the variance between dyno pulls

...so really, it's all just theory

Is this theory worth hacking up my FM cast DP section to make it emulate a bell mouth? Maybe something to try if porting IWG doesn't work for creep

eh... i don't think it would hurt performance enough to really matter but at a glance the fm cast unit doesn't look like it has a blockage issue. The mouth is quite large and appears to have plenty of clearance.

Has your 2560 wastegate PORT been ported?

you need to port your hotside. the 2560's didn't come with any sort of channel in them like the 2871's did (newer hotside design)

make sure you do both: open up the hole, and make the channel. we have threads on this

the fm elbow shouldn't be your problem

Not yet. I just got off the phone with Stephanie at begi to talk about it. Not sure if I'm going to attempt it myself or send it to them ($75) but it's definitely the next step to solving my creep

LownSlow I think you are better off looking into porting. From my reading that seems to solve most people's creep issues on similar setups. Thats what I would do if I were you anyways.

Those EFRs are awesome. Do want.

I get carbide burrs in the mail today. Ill probably have the car back on the road this weekend and see how well opening up the wastegate hole a little and smoothing out the current port job does. I think krissetsfire is onto something though. I bet the flapper itself is blocking flow when open.

I type too slow^ thanks 18psi

When you buy a turbo kit from BEGI one of the things they do as part of their setup is port the turbo if it is one that needs it. I got my 2560r from them and Corky did a fine job with getting it to flow properly.

Before I modified my downpipe I would creep from 6 to 8 after i upgraded to 3" exhaust. 2.5" exhaust was maybe half a psi creep.

so that means good work on the turbo port.... mediocre on the dp

Your dyno suggests that yes, you will break it.

Dann

https://www.miataturbo.net/attachmen...ine=1460850167

18psi, braineack, any other smart people:
I took apart the turbo to port the wastegate begi style. My question: should I smooth out the inside of the FM downpipe while I'm in there? You can see where the exhaust hits the casting as it makes its way out the upper hole in the picture

https://www.miataturbo.net/attachmen...ine=1460850374

Quick scetch of the parts I'm considering taking out. I could also round off all the other sharp edges on the other side

Just put the car back together after opening up the wastegate hole and smoothing out the channel Begi made. Results? Car feels incredibly slow :party: Peaked at 12-14psi where it peaked at 16+psi previously and it made ~2psi less everywhere after turbo spooled. VD puts the power around 240hp on a dynojet. AFRs were very rich so I'll have to retune WOT but I assume after they are dialed in I will be right around 250 again. I can't comfortable run a MBC to help spool anymore (its kinda terrible right now) but if it keeps my motor alive I am a happy camper.

Thanks everyone for your contributions in this thread!

not really needed for your application. I honestly wouldn't make it any thinner if I were you
your wg "port" on the elbow is more than enough
:likecat: great, glad it worked