Max PSI

[DaleNixon]

How difficult is it to see 15.6PSI on a boost gauge? Do you have to really romp on it? With my car, it seems to take considerable effort to get anything above 10PSI. Last night I took 4th gear to 60 at I'd say 1/2 to 2/3 throttle, and I held about 11PSI on the Dashhawk. Do you have to go WOT at certain rpm ranges in order to see a sustained 15PSI?

Maybe I have a leak, but I've checked every hose. Intercooler hoses, turbo inlet (when I installed my Cobb, intake, etc. I have a Forge BPV and I've been adding shims to the blue spring. I'm at 2 shims now but I had 1 shim in last night when I hit 11PSI.

Do I just need to man up and do some hard WOT runs or does it sound like I have a problem? Thanks for helping a turbo noob out.

[AndyMS3]

You should spool to 15.6PSIG in no time especially under 4th gear load. The K04 spools very fast so something is acting up somewhere. What's you're LTFT at right now (idle, cruise, WOT)?

Do a boost leak test to locate pesky leaks. Even though you checked all your hose connections doesn't mean that there isn't any leaks.

[DaleNixon]

My LTFTs are ridiculous... always have been with the Cobb SRI.

idle is like +10.
cruise is like +8.6.
WOT is around +14.

How do I perform a leakdown test?

[AndyMS3]

Originally Posted by DaleNixon How do I perform a leakdown test?

I edited my post, I should probably call it a boost leak test as leakdown is usually a term used for an engine leak test.

To perform a boost leak test, you need to make a rig like this: Boost Leak Tester - and hook it up to the compressor inlet on your turbo. I'm not sure about the OD on the turbo inlet, I think a 2.25" ID piece of rubber hose would work but maybe someone else can chime in on this as I haven't pressure tested my system yet.

Build the rig like you see in the picture and pressurize your system. When ever I suspected boost leaks on my DSM, I would use a really soapy solution and a sponge to dab the soap on hose connections carefully watching for bubbles. Also as recommended in that page I posted, having a second set of ears is always helpful.

[AndyMS3]

Originally Posted by DaleNixon My LTFTs are ridiculous... always have been with the Cobb SRI. idle is like +10. cruise is like +8.6. WOT is around +14.

If you had a larger leak, I would suspect a lower if not negative number for your idle and cruise LTFT's as your system is in vac.

Reading those figures my best guess would be your little leak is turning into a big leak while under boost.

[DaleNixon]

Cool link! I'll check that out. In the meantime, are there any risks associated with a leak if I do have one? I think the car's been like this since I got it brand new. I'm at 4800 miles now.

But just to verify, you're saying I should hit 15.6PSI even at 1/2 to 2/3 throttle in 4th gear up to 60MPH?

[AndyMS3]

Originally Posted by DaleNixon But just to verify, you're saying I should hit 15.6PSI even at 1/2 to 2/3 throttle in 4th gear up to 60MPH?

If you are shifting - leaving from 3rd to 4th at 3000rpm and going 1/2 to 2/3 throttle till about 4000rpm in 4th, you should see max boost. If you slowly rise the throttle you may not see max boost. Just put a lot of load on the engine and record boost as you may not be loading up enough.

[AndyMS3]

Originally Posted by DaleNixon Cool link! I'll check that out. In the meantime, are there any risks associated with a leak if I do have one?

Oops forgot to respond to this. The danger depends on severity but based on your LTFT's, especially at WOT I would try to find the problem sooner rather than later. It's never good to have unmetered air entering or metered air exiting your system. Just watch knock and your LTFT's.

[DaleNixon]

I'm assuming you mean UNmetered air. With my stock airbox or my old HKS intake the LTFTs are perfect. It's the Cobb SRI that drove them all crazy. But there are numerous threads on what the Cobb SRI can do to your LTFTs.

I was in touch with Cobb about the high LTFTs I've experienced with their intake. At first they really wanted to help. Now they just ignore me completely. And I still buy new products from them. I guess I'm a sucker.

[AndyMS3]

Originally Posted by DaleNixon It was about 45F last night when I did the run. And I always build acceleration slowly. I'd say I shifted from 3rd at about 3500 rpm. Started with little throttle then worked my way up to 1/2 to 2/3. It's possible I'm just babying the car too much. And yes, I reset my ECU about 200 miles ago when I installed step colder plugs and an ETS intercooler.

Lol cmon man your car doesn't have glass wheels, give that shit some throttle. Load it up and take a look but it sounds like you aren't loading up the engine enough.

If you do load up and are still seeing below 15.6PSIG, do a boost leak test for sure. Especially after installing a new component into your air tract.

Originally Posted by DaleNixon I'm assuming you mean UNmetered air. With my stock airbox or my old HKS intake the LTFTs are perfect. It's the Cobb SRI that drove them all crazy. But there are numerous threads on what the Cobb SRI can do to your LTFTs. I was in touch with Cobb about the high LTFTs I've experienced with their intake. At first they really wanted to help. Now they just ignore me completely. And I still buy new products from them. I guess I'm a sucker.

Sorry I meant metered air leaving (positive boost leak) or UNmetered air entering (negative boost leak).

I seem to see more threads on the Cobb SRI's - perhaps the ID is to larger/small or the MAF isn't sitting flush? I wouldn't be able to guess as I've never handled one before.

[phantom6294]

Originally Posted by DaleNixon My LTFTs are ridiculous... always have been with the Cobb SRI. idle is like +10. cruise is like +8.6. WOT is around +14.

Originally Posted by stratum If you had a larger leak, I would suspect a lower if not negative number for your idle and cruise LTFT's as your system is in vac. Reading those figures my best guess would be your little leak is turning into a big leak while under boost.

Positive LTFT across the board should lean (no pun intended) towards a pre-turbo leak. In that case, the car is always ingesting more air than is being sensed by the MAF. If the leak is post turbo, then most likely when the car is in vacuum (idle/cruise) you would be ingesting more air (positive fuel trim) but under boost you would be leaking air out (negative fuel trims). This of course ignores the effect of any changes to the intake tract (i.e. COBB SRI) -- for all I know, those kind of LTFT are normal with the COBB SRI.

[802MS3]

yup. have you recently reset your ECU? Last time I reset mine (when I installed my turbo inlet) It took a good week or so to get my full boost back. Also has it been cold where you are? This car doesn't really like to hold 15psi when its below freezing outside

[DaleNixon]

It was about 45F last night when I did the run. And I always build acceleration slowly. I'd say I shifted from 3rd at about 3500 rpm. Started with little throttle then worked my way up to 1/2 to 2/3. It's possible I'm just babying the car too much.

And yes, I reset my ECU about 200 miles ago when I installed step colder plugs and an ETS intercooler.

[mazdaj]

i dont even have to go wot throttle to hit my target boost whether it be 15.6 stock or 17.5 on my standback. there is something about this ecu that seems to open the throttle plate for a split second even before i go wot, i have no dh logs to back this up, but its something ive noticed. if im 1/4 throttle, say in 3rd gear, and i go to 3/4 throttle very quickly, my boost usually hits 15 or 17 (whatever i set it to).

i think you may have a boost leak, do you have a dh to show some logs?

[DaleNixon]

I do have a Dashhawk. I'll run some logs and post them in this thread later. I guess I'll log Boost, AFR, LTFT, Pedal Position, and RPM.

[AndyMS3]

Originally Posted by DaleNixon I do have a Dashhawk. I'll run some logs and post them in this thread later. I guess I'll log Boost, AFR, LTFT, Pedal Position, and RPM.

Instead of pedal position log wastegate duty cycle so we can make sure you're system is seeing full boost.

[DaleNixon]

Will do.

[mazdaj]

wastegate duty cycle

what he said ^^^

[mazdaj]

dude, wot that shit and then tell us if u hit target boost.....the boost doesnt build with progressional throttle. its all or nothing on this car (not really, but u have to quickly give it throttle instead of gradually)

[DaleNixon]

Is loading it up with the pedal to the floor in low gears (3rd, 4th) at 2500+ safe?

[AndyMS3]

Originally Posted by DaleNixon Is loading it up with the pedal to the floor in low gears (3rd, 4th) at 2500+ safe?

Datalog from 3000rpm in 4th.

[DaleNixon]

4th gear 3000rpm, WOT, all the way to redline or at least 5800rpm?

[mazdaj]

do it at 3k instead, thats where our torque is

[DaleNixon]

So get to 3000 and FLOOR that shit? Sorry for the newb questions.

[mazdaj]

yes, do a log until about 5500rpm, no need to go any further.....u can do it in 3rd or 4th

also, hold on to the steering wheel tight if youve never done this before lol =)

[mazdaj]

you've got yourself a deal, i'll take it

[DaleNixon]

I can't log until tonight after I get off work Hopefully River road isn't too crowded.

[DaleNixon]

I made a log. 3000 RPM to about 4700 at WOT... I didn't have a lot of road to work with. I spiked at around 18PSI and sustained between 15.6 to 16.3 for about 4 seconds before I had to let off:



Sorry for the HUEG image.

I guess I just wasn't pushing the car hard enough to see peak boost before. I do tend to baby it a bit. Doing this log was quite a rush!

Edit: On subsequent runs the boost only peaked to about 15.3PSI and tapered off to around 13PSI. What would cause that? Heat soak? My best run was the first one I did, which is shown in the log above. The car felt super strong on each run I did.

Here is a log from a later run:

[DaleNixon]

Bump! Dudes, do those logs look healthy to you? Thanks!

[AndyMS3]

Your AFR looks high for an untuned vehicle, boost seems to taper off following the WGDC, can't see the LTFT.

Try rescaling your log and unhiding the 5th PID (LTFT).

[DaleNixon]

Boost tapering off with WGDC is the desired effect, I take it? You can see LTFT in the first log.

My AFR always has seemed kind of high to me. There's nothing unusual about my knock retard though.

[phailerider]

first log looks great. second log you didnt have it on the floor, wot did you?

i just read this thread and its alot of laughs. You flooored the car and it was a "rush"? dude... stomp that motherfucker. your boost will be fine if you actually open up the car.

[DaleNixon]

Hehe yea I know I look ridiculous here I'm still learning this stuff, and I appreciate any input you guys have.

On the second log I probably didn't have it all the way to the floor. This is the fastest car I've ever driven. No lie.

[phailerider]

Originally Posted by DaleNixon Hehe yea I know I look ridiculous here I'm still learning this stuff, and I appreciate any input you guys have. On the second log I probably didn't have it all the way to the floor. This is the fastest car I've ever driven. No lie.

heres how you do logs.....

1. have a beer to loosen up
2. wait until the sun goes down and traffic is at a minimum
3. find a lonely spot and floor the car
4. go look at your logs
5. have sex
6. repeat

[802MS3]

Originally Posted by palerider heres how you do logs..... 1. have a beer to loosen up 2. wait until the sun goes down and traffic is at a minimum 3. find a lonely spot and floor the car 4. go look at your logs 5. have sex 6. repeat

best advice ever

[DaleNixon]

Yes sir! I'll keep that in mind for future reference. I was one nervous bastard doing this run. It was the only lonely spot I could find and it was a narrow road with HUGE ditches on either side running right along the Mississippi river in good old Baton Rouge, Louisiana.

[ATAZ]

#5 and #6....heh heh allllriiiiiiighhhht!

[DaleNixon]

I'm not a very experienced performance driver, but I've been driving boring cars for 14 years.

Good point about the excuse... "sorry officer, I was datalogging at WOT in 4th gear to analyze my LTFTs and AFRs". Haha!