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For sake of discussion see the below M/E log & v-dyno pairs.
The first first log & v-dyno pair was tight, no leak, and at ~ 12 psi. 370 HP/ 251 lbft
There was likely a small leak on the second log & v-dyno pair, ...but for sake of discussion can we presume the system was sealed tight during this pull. Peak boost was 13.x psi. 314 HP/ 265 lbft
What can you discern regarding the engine nearing flow capacity from these?
Firstly .... much better to increase the size of the chart so you can see it better (I use the 2.5 times button)
I think you can forget the second chart because of the leak .... the amount that it exceeds the first chart suggests it's more than a small one.
The first chart is showing a leveling out at 7555 and , although it's not reached the point where maf reduces thereafter . I'd still recommend dumping boost there because from there on the amount of exhaust gas carryover is increasing. On a dyno you would probably see power peak a few hundred rpm after that point but for the sake of safety I'd still dump at that point.
Firstly .... much better to increase the size of the chart so you can see it better (I use the 2.5 times button)...
Aaah, had not noticed the M/E zoom buttons. Learn something new every day.
Originally Posted by Brettus
...The first chart is showing a leveling out at 7555 and , although it's not reached the point where maf reduces thereafter . I'd still recommend dumping boost there because from there on the amount of exhaust gas carryover is increasing. On a dyno you would probably see power peak a few hundred rpm after that point but for the sake of safety I'd still dump at that point.
Ok, so after eliminating variables, e.g. leaks, boost drop & creep, you are evaluating the mass flow (MAF) curve to identify the point where the curve plateaus: the unique point on each system beyond which the pressure of the recirculating combustion gases limit further increase of mass flow safely.
Yes ....... what I've noticed is (provided the turbo will flow enough) ...the more inefficient the system is ........... the higher in the rpm range you actually reach that point . Your system looks pretty good IMO as it's seeing that point quite early which means you can raise boost and make more torque throughout the range.
Yes ....... what I've noticed is (provided the turbo will flow enough) ...the more inefficient the system is ........... the higher in the rpm range you actually reach that point . Your system looks pretty good IMO as it's seeing that point quite early...
Well, that's definitely good news. ... but you lost me here...
Originally Posted by Brettus
... which means you can raise boost and make more torque throughout the range.
Yeah .... I didn't explain that too well
Really I just meant that , so long as you cut boost at the right point as discussed, you can keep raising the boost and make a really good power curve. If you don't cut boost or limit the revs ...eventually the engine will blow at high rpm.
With an inefficient system you can actually rev it a little higher at the same boost but will make less power and be stressing the engine and all the cooling systems more in doing so.
Yeah .... I didn't explain that too well
Really I just meant that , so long as you cut boost at the right point as discussed, you can keep raising the boost and make a really good power curve. If you don't cut boost or limit the revs ...eventually the engine will blow at high rpm.
With an inefficient system you can actually rev it a little higher at the same boost but will make less power and be stressing the engine and all the cooling systems more in doing so.
Roger that...
We've discussed some strategies to cut boost. I need to get that done.
Another To Do list is materializing re: electronics:
- Re-plumb EBC control line pre-throttle
- Wire AEM Failsafe boost cut
- Wire boost cut @ 7500 rpm
Went back and reviewed the "Where Did You Plumb Your BC Signal Line To" thread and can see where pre or post TB can work.
If plumbed pre-TB, the BC alone controls the intake pressure...regardless the TB position.
If plumbed post-TB, a good BOV...set properly...w/recirc is required to do the same job.
When the TB is open, intake pressure is governed by the BC alone...similar to the pre-TB config.
But when the TB is partially or fully closed, the BC sees a differential up to full vac..., the turbo continues to spool and build pressure in the intake..., and this excess pressure, I.e. above target boost, m/b released by the BOV. The BOV m/b recirc'd to avoid jacking w/AFRs. If the BOV or its control lines fail, intake pressure spikes will occur.
While both can work, and I had no issues w/mine plumbed post-TB; I concur simplicity dictates pre-TB s/b superior.
If plumbed post-TB, a good BOV...set properly...w/recirc is required to do the same job...
It's true that a 'good' BOV will help prevent too much pressure building pre throttle and maybe in your case that's all that's needed. I like to try and make things work as good as they possibly can though ..... and for that reason prefer to put the control line pre throttle.
I actually spent a **** ton of time playing with this to reach the conclusion I did. Mainly because all the conventional wisdom suggested I do it the other way around. It was about then I started to realise that conventional wisdom isn't always best
... Another To Do list is materializing re: electronics:
- Re-plumb EBC control line pre-throttle
- Wire AEM Failsafe boost cut
- Wire boost cut @ 7500 rpm
Meanwhile , I'll limit revs...
As I began thinking thru the cutting boost at 7500 rpm strategy...it dawned on me that when initiated... boost will drop to WG spring pressure 9#. Nice!
As I began thinking thru the cutting boost at 7500 rpm strategy...it dawned on me that when initiated... boost will drop to WG spring pressure 9#. Nice!
Yep ..... of course !
Although mine wg spring is only 5psi which gives me extra safety because it activates when afrs go lean or boost goes too high .
Yep ..... of course !
Although mine wg spring is only 5psi which gives me extra safety because it activates when afrs go lean or boost goes too high .
I was hoping to keep my WG spring at 7.5#...for safety, but it became a limiting factor to achieving my target boost w/my EBC solenoid. So, recently increased to 9#. Now, I believe when failsafe is activated... 9# will work out nicely:
You will barely notice the transfer . My cut is very noticeable , but i don't mind cuz it's a good way to know when to change gear. Useful when in the heat of the battle on track
You will barely notice the transfer . My cut is very noticeable , but i don't mind cuz it's a good way to know when to change gear. Useful when in the heat of the battle on track
Still exhibiting a boost leak on pulls of target boost above 13psi ..., but she managed the below pull tonight: @ 13.6 psi peak...trailing to 12.3 psi, and 380 g/s max @ 7966 rpm.
Pleased..., but still working to eliminate the leak to ease turbo load, and better sustain HP/torque thru the rev range. So, I purchased a new hump coupler for the charge to TB connection. I'll get that installed over the next few days and see if it results in reliably sealing above 13 psi.
A spirited drive today indicates she's holding 13.5 psi. I believe that the combination of heat cycling of the coupler and putting a 1/4-1/2 turn on key clamps after each drive... while hot... has resulted in better sealing. Now, I don't want to touch a thing.
On the below pull today boost rise peaked at 13.46, and increased to 13.59 psi thru the rev range. Pretty stoked at this result.
01-09-2020, 11:03 AM
..., but she managed the below pull tonight: @ 13.6 psi peak...trailing to 12.3 psi, and 380 g/s max @ 7966 rpm.
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