Megasquirt Boost
 

Couple of boost questions I'm trying to understand:

I've set my KPA to 180 and that gives me a max boost of 11.5 psi at approx 6400 RPMs

1. The boost doesn't hold a steady 11.5 psi just gets there and then the fuel/spark cut hits and it drops. Is there a way of just holding max KPA without the sudden drop off?

2. If it revs upto 6400rpm on 11.5psi would there be any gain by lifting the KPA limit to 200 to raise the boost? With the max power output supposedly 6400rpm before it starts to drop off would I see 15psi before the rev linter kicked in at 6800 ?

I'm not really understanding where the gain is felt by increasing the KPA to get the boost to say 15psi when it takes 6400rpm to reach 11.5psi, or does it get to 15psi just as quickly ??

Bit of a garbled question but I hope you understand what I'm asking.

Thanks and pointers would be welcome.

If you're taking 6400 Rpms to reach 11.5psi, you've got a leak, a turbo that's too big, or no boost control.

You should reach target boost in the 3000-4000rpm range, and if you increase that target, you'll see max boos slightly later, maybe 100-300rpms later depending on turbo, then that target will be held until redline.

Ah ok, I've got the garret 2560R Flyin Miata Spec turbo.
Also used an EBC with it set at 100% so wastgate only control to get my min which is 10.5psi. With just a few % off on the control settings it gets to 11.5psi. So I think that means the EBCs working. So leak is the probable cause?

Thanks

You're not talking about overboost are you?

If you can tell me how to post a picture I'll send a pic of the log, I could post a log file if I knew how to do that too.

Open what you are setting so it's up on the screen.
Press the print screen button.
Open MS paint.
CTRL+V.
Save.
Upload.
Post.

hmmm, im one of the plonkers with a Mac I cant use..........

Then do the mac equivalent. Don't tell me you cant, because i know it's possible.

https://www.miataturbo.net/attachmen...ine=1392248772

Above with rpms at 4000 and boost just over 5psi (these are WOT pulls in 3rd)

https://www.miataturbo.net/attachmen...ine=1392248772

Above with rpms just over 6400 and boost just over 11psi (these are WOT pulls in 3rd)

Like I say it never holds a steady boost level on any of my logs.........

Looks like a classic case of boost creep on the 2560.

Was the wastegate ported at all?

Edit* you can post the log too. Just upload it using this sites uploader... I don't think i'd need Mac software to view it, i don't think. Maybe someone can confirm.

This is what if read about boost creep and it didn't seem to relate to what I was seeing at all ?
Boost creep is a condition of rising boost levels past what the predetermined level has been set at. Boost creep is caused by a fully opened Wastegates not being able to flow enough exhaust to bypass the housing via the Wastegates itself. For example, if your boost is set to 12psi, and you go into full boost, you will see a quick rise to 12 or 13psi, but as the rpm's increase, the boost levels also increase beyond what the boost controller or stock settings were. Boost creep is typically more pronounced at higher rpm's since there is more exhaust flow present for the Wastegates to bypass. Effective methods of avoiding or eliminating boost creep include porting the internal Wastegates opening to allow more airflow out of the turbine, or to use an external Wastegates.


I thought my logs were showing a really slow boost rise which never reached it's maximum.

If you have a really slow rise to peak pressure, or your boost is a linear line climbing all the way to red line, then you have a boost leak. Check vacuum lines, couplers, clamps, etc.

Make sure your boost protection is above your target maximum boost. If you want 11.5psi, you'll want to set your over boost protection to 12.5 or 13.5, especially while tuning in your MBC or EBC, since you'll just hit a wall every time you try to adjust it.

Yeah, he's right. I didn't look at it closely enough.

Thanks for the help, think I'm ready for a leak test with my homemade bungs and valve point made, just need to clamp them up and add attach the pump.....

https://www.miataturbo.net/attachmen...ine=1392314611

https://www.miataturbo.net/attachmen...ine=1392314611

https://www.miataturbo.net/attachmen...ine=1392314611

Pretty Cool pressure tester fab... Impressed actually.

Cheers, what I'm unsure about is where I should be bunging !!! Some YouTube vids say just put a single bung in the turbo inlet and blow air in through there. Others say bung the pipe from the turbo outlet and bung before the inlet manifold and blow air in at the turbo outlet pipe. Safest seems the later which I'm trying but that's not testing the turbo or any of the engine / manifold gaskets etc. Any recommendations ? Am I going about this the right way or wrong way? Thanks

When i did mine i didn't bung anything. Put my tester on the turbo inlet and pressurized.

TB open and TB closed.

You should be able to hear leaks. Some might escape out the exhaust, and into the valve cover.

https://www.miataturbo.net/attachmen...ine=1392386626

https://www.miataturbo.net/attachmen...ine=1392386626

Ok leak test done and there's one hell of a leak on the BOV. I don't understand the internal workings of these things TBH. It's leaking from the join in the casing next to the tiny hole in the side you can see in the photo. The whole barrel spins around, always has but I assumes that was normal.

That would definately have something to do with it.

Can you find information about your BOV online anywhere?

That said, the BOV is SUPPOSED to vent when there is less pressure on the manifold side than there is on the charge pipe side. The next step is to hook everything back up and check to see if your BOV is venting when the engine is running. If you have two people, have your helper rev the engine without a load. If you have air venting out of the BOV while revving then you need to play close attention to the BOV. IF it doesn't vent until the helper lifts (and you get a "Whoosh" sound) then it is working properly.

Let us know.

https://www.miataturbo.net/attachmen...ine=1392396828

No helper needed, just spin the little bronze wheel in the right side of this picture and the engine will rev.

Well it's official I am a plonker. The BOV spinning around isn't spinning around it's unscrewing. How do I know this ? Because I kept turning it one direction and it threw its contents across the garage spring and all. Dooooh
So tighten that all back up, refit all the pipes and hopefully problem solved. On a plus this will be the cheapest 5psi increase at 4500rpm I'll ever get...lol
Thanks for all your help guys

Yeah, with how you hooked up the boost tester its going to leak out of the bov. You need to pressurize the nipple on the bov with the tester, either by just leaving the ic piping connected to the throttle body or by running the bov hose to a barb on your tb side plug.

I've fastened the inlet manifold back pipe back on for the test and am just using the one bung with the valve now and the BOV is a recirculating one so it puts the air back in after the bung. It really is just leaking out the threads between the two barrels but I'll do another leak test once I put it all back together.

Can someone help clarify: if from a standing and floor it 100% throttle should I be hitting target boost at around 4000rpm if there are no leaks, turbo is correctly sized and my EBC is functioning correctly?

My 1.6 with a slightly small sr20 turbo hits full boost of 11psi in the mid 3000s. I'd expect low 3000s if it's a 1.8 with EBC.

I'd hook up the leak tester and keep looking.

Hmmm thought you might say that, thought I had tested but maybe it didn't push the pressure high enough. Back to the leak test then 👍

Are you pulling your boost source from the correct place for your gauge? If you're getting goofy boost readings I would start there.

I'm taking it from the inlet mani to the megasquirt.

http://i1063.photobucket.com/albums/...0B95B788AB.jpg

http://i1063.photobucket.com/albums/...3C77485546.jpg

Found 3 leaks now, lessons still being learnt, when you buy a used turbo kit fit new clamps.....

Did a final leak at 10psi

http://youtu.be/Ly_67xxVJ5I


Just need to go out and log it again

Well I've logged it again and I'm still at 6psi at 4000 rpm from a standing start. Puzzled as I did have several leaks I've stopped. I've done a leak test up to 12psi and it does hold what I think is reasonably well. It drops to 8psi after about 60 seconds, there is air going somewhere but it sounds like it moving around the inlet manifold.

And these are 3rd gear pulls? 4th would be better but we realize 1500-7000rpm in 4th gear is a little illegal.

1st and second happen so fast your turbo won't have time to build boost.

Have you tried running just waste gate pressure? Or a simple mbc?

Now then I need to understand that better, I may be aiming for the impossible then.
I need to put a log on here for you to look at I think. Is it easy to put a file in the forum?

Yes, hit "post reply" instead of the quick reply message, and you'll get a lot more options. Then click "manage attachments" and add your .msl file.

Logs from pre leak and post leak attached

Still on with the leak testing and I'm hoping you can clear up the how to do it right question. I'm just feeding 12psi of air in through the turbo outlet pipe and I've definitely no leaks up to the manifold intake after fixing 3. What I'm not sure about is what happens after that. Think I need an internal combustion engine lesson!!
Seems like the air filled up the space after that then leaked from the manifold breather pipe, then it stopped. The bung into the rocker cover doesn't seem really air sealed anyway?? Is that because air shouldn't be reaching there? I'm thinking all I need to test is before the TB.
The outcome is it loses the pressure but takes about 60seconds but there's no obvious hissing sound?
Done more logs above but there's no change as in I'm not hitting max boost at 3000 to 4000 rpm range.

Getting some results
 

Finally getting some results, got my EBC table working and what a difference already. The EBC sounds like a jack hammer in the cab ! not sure what that's all about..... but the grin is back

If your EBC is "knocking" it is because your settings are wrong. It's been awhile but try a different frequency I think... Which EBC controller are you using?

I'm using one I bought from DIY Autotune, Im told it will be loud under operating conditions and I've got it operating at low RPMs and TP at the moment but even at 3000rpm it was really loud. I've moved it forward in the engine near the air filter and it much more bearable 👍

Mine is silent... Well more silent than my engine. Just out of curiosity, where are you getting your wastegate signal line from?

https://www.miataturbo.net/attachmen...ine=1392844876

Arrow pointing almost to the wastgate feed.

The reply I got about the EBC from the retailer was:

It is normal for it to click when it is operating, however it does not need to be operating at all times. A value of zero duty in the duty table will kinda turn it off in areas where you do not need it to be operating.

You want it pre throttle body. Like, right before that 90* elbow pictured.

Bugger, I've my boost Guage, my Wastgage line in and my megasquirt all getting their signal from the inlet manifold !!
Are they all wrong then ?

Wastegate actuator signal line should not be plugged into intake manifold. Wastegate actuator is NOT designed for vacuum. You may have blown out your actuator which might account for why you aren't seeing boost like you should.

EDIT: with a properly set up EBC you might be able to deal with it, but if you ever run straight wastegate (for example during warm up) your actuator is seeing vacuum.

Ok got that thanks, I'm wondering now if I've got the answer I just gave for the wastgate signal line wrong. I will have to check tomorrow. I've got it in my head there may be a brass fitting on the turbo outlet it's connected to !! Does that sound likely ?
Now I've just googled it though that sounds like it's not ideal as it should be after the IC but before the TB.

Likely.


Not ideal, but not harmful. Anywhere before throttle body is safe. Anywhere between IC and throttle body is ideal.

If you're using electronic boost control you can connect from anywhere between the compressor outlet and the throttle body. The location near the throttle body is only critical for manual boost controllers or no boost controller.

Ah that's good news because I am using an EBC and it is getting the line in from the turbo outlet.
Thanks guys, now just need to tweet the boost duty figures.