Automatic car, that ALWAYS makes boost rather quickly, and holds it steady throughout a run.

At a T&T the other evening, got bad tire shake (along with bumper cover and hatch shake, lol), so let out of it, then hit it and finished the run to get a MPH, at least...ET was a throwaway due to the wheel hop/tire shake, but it was DOWN 10 MPH!

Run 1, steady 19#, once rolling, went 147.89, also a semi aborted, tire shaking run
Run 2, same as above, 19#, went 147.53
Run 3, peaked at 16# sloping down to 12#, only went 138

Loaded it up and headed home, since track was an ice rink...

Next day, on the lift...
Checked over all wastegate lines...I run dual 44mm gates, with 4 port MAC, TurboSmart EBoost Street controller
Made sure boost controller wasn't somehow changed, although anyone who runs a Turbosmart, knows you can barely make a change on purpose, LOL
No leaky exhaust, or blown head gasket, charge pipe off, or any of that.
Only issue I saw, was my air filter has came off turbo inlet...On or Off, it's never made a difference in boost, but I run it full time.
I even checked impeller to make sure shaft wasn't broken from the tire chatter episode.

Any ideas on what to look at, that I am missing?

My DEFAULT "Boost Group" is BG1, which is 10#...BG2, is 19#
I originally thought I inadvertently shut the engine off, and simply forgot to hit the button, to go to higher boost level...But car doesn't spike with the dual gates, so I'm at a loss...

Tune was the same on all 3 passes...

Complimentary severe tire shake video, in slo-mo for your viewing pleasure



And full shot/full pass in this video, Fast Forward to 3:30 in.

 

Well...no idea where the boost went, but it seems to have returned, LOL...
I guess I forgot to hit the button, to put it on Boost Group 2, aka, the higher one...

FWIW, Since a 1mph gain is not worth the 100 extra decibels, I removed the 4" downpipe, replacing it with what I have been running all year...a 3" one, with cutout. I also swapped on an On3 stainless "catback", which surprisingly, fit well, and sounds great driving. Sounded like a European sports car revving it in my shop....but sounds 1,000% better, on the road, with some turbo noises going through it...


.

 

Be neat to see how much MPH the exhaust kills.

 

Might do a same day, back to back next year. I have probably one more chance at a new best to end this year with, so gotta keep that cutout open, lol.

Best so far, a month ago, was a [email protected], footbraking. Hoping for a 9.5x and/or 150. I think the little 78/75 can do it.

 

Slow day at work, so looked through my Log Book, and saw what the losses were between open 3" cutout, and Jeg's catback (which has to be more restrictive than what I have now).

Was a year ago, but SAME DAY, and back to back...

9/5/2020, both runs leaving like a turd, off idle, on 6# w/g spring, trying to dial in & run an 11.50 index class

9:24am - 11.05 @ 133.79, 1.94 60', and 7.34 @ 103.41 (660' numbers)

9:37am - 11.72 @ 121.83, 1.99 60', and 7.67 @ 96.42 (660' numbers)

So, even at low boost, car lost 8mph and nearly 7/10ths in ET.
Not a whole lot of faith in most of the Wallace Racing Calculators, especially on a boosted car, but they say:

4000# race weight
HP by ET = 594.74 vs. 498.46, or 96.28 hp loss through exhaust
HP by MPH = 749.19 vs. 565.70, or 183.49 hp loss through exhaust

Assuming the 96hp loss is even close, I can't imagine how much it'd choke at triple the boost, lol.

 

A boost leak can cause lost power, engine damage. Air leaving the plumbing post compressor causes a rise in EGT, EGP, and IAT, and excessive impeller wheel speed, which may lead to engine failure, turbo failure, and always causes lost power. It may also cause a drop in boost pressure if the compressor is unable to keep up with demand.

Always pressure test (boost leak test). I have a great video online of performing the test if you want I can post it.

 

Would love to see the video, and I am sure others would like to see it also.

FWIW, last weekend, the disappearing boost returned...Evidently, I never hit the button on my controller...

9.68@148 with a very lame 1.78 sixty foot.

FWIW, with the exhaust it feels like it runs as well as an open cutout

 

I perform the pressure test on my daily driver


Every forced induction application needs pressure test and also as routine maintenance, say every couple oil changes, when setups are fresh especially.

 

Cool video.
Will this still work if the cam has a good amount of overlap as it would/could escape through the exhaust valve?
Or am I missing something? Which IS possible!

 

I've pressure tested hundreds of engines. There is no issue.

They all leak something through an intake valve because an intake valve is always open pretty much. And the rings will leak something even if the engine isn't in an overlap. Nevertheless, the flow rate through rings and a cracked exhaust valve is very low, it should not impact the pressure test. If you listen close in my video you can hear air escaping from the engine internals- this accounts for the pressure drop through the system. Otherwise it would have had the same pressure all over, like a tire. So, my engine did leak significant pressure through a cylinder (enough to cause 6-7 psi of pressure drop from compressor cover to intake manifold) however the compressor tank was plenty large enough (standard size, nothing fancy) to keep up with the demand and we simply dialed up the pressure until the intake manifold hit it's target 'boost' which in my case 22psi was plenty. That put the compressor cover at like 27psi probably. But in a real scenario with the compressor making actual boost to provide 22psi to the intake manifold, it would have to be higher at the cover outlet by a similar margin (+5psi or so) thus the engine leaking down is actually going to pressure test the system in a more realistic fashion (27psi -> 22psi for example from beginning to end) as opposed to setting the entire thing to one number like a tire.

 

To put this into another perspective. In the business of tuning turbocharged engines, hundreds of them, you quickly learn never to tune one until its had a pressure test. It is an absolutely essential test before tuning the engine. I let ONE guy, ONE time opt out of it, I made him sign a waiver and everything before we went to the dyno. Dude just didn't want to do it. Well it had a massive boost leak and you don't hear the leak with the engine roaring 7k rpm. Some of the pistons seized in the bore from high EGT and IAT due to the massive leak, on gasoline it doesn't take much to generate that kind of heat. Every since then I don't even allow people to opt out of the test anymore. It isn't worth my time.

 

A massive leak will show on iat's, and boost response if you know what you're looking for. There's nothing wrong with pressure testing, but imo, any tuner worth the money you're paying them would catch high iat's (whatever may be causing them) before it becomes catastrophic.

 

The IAT is not a reliable source.
1. Some setup do not run intercooler and expect 140-180*F IAT.
2. Other run too small of intercoolers and 130-140*F Is normal.
3. Some large turbos which can handle increased flow rates without much iat rise- those setups gain EGT & EGP much faster than IAT.

That last one is typical for V8 crowd who tend to choose oversized turbos which run near the center of the map- making the boost leak push to the edge but still on the map means the car still 'flys' even with a large leak and high IAT. The owner becomes a victim of the leak and unaware of the issue robbing power. As to boost response, they would never know how good it could be if they never pressure tested to realize the difference. Most just accept the response whatever it is without question. You are correct that if you 'know what to look for' like I did with my leak (rising IAT and lost power) but not everybody is a super sensitive cautious detail oriented etc...it takes alot of experience and tuning variety of setups IMO and most people (the ones the video is for) are so new to turbos they never even heard of a pressure test.

Main issue is EGT and EGP, residual heat and pressure near post combustion chamber, causes excessive piston expansion and ring gap closing, over heating of cylinder walls and internal components. You can also overspeed the turbo and cause it to explode violently I suppose but I've never seen that happen, only know its possible.

High IAT can only cause a negative effect with fuel, which is only an issue if fuel quality is poor. In other words, high IAT + C16 race fuel = no detonation or fuel related issues which means the engine will still appear to run normal, while it is overheating due to high EGT and EGP. Throw in forged pistons and you basically mask the issue completely thanks to excessive piston/wall clearance and ring gap.

To put it another way, combustion temp is 2000*F or near that. High IAT of say 200*F is negligible to combustion temp.

My personal suggestion for IAT on gasoline is no more than about 112-115*F IAT. My car may see 106*F maybe 110*F max after a full 1/4 mile in the hottest possible weather in Florida, peak ambient temps in July. Using a very "small" turbo.

 

What type of intercooler and how much boost to be in the 110* range?

 

To start with, if you are new, For up to 750-800bhp I like to start out with and use a generic 3"x12"x31" (or 3x12x30+) Ebay intercooler approx $115 shipped

After a few years of tweaking the setup and hitting the intercooler with rocks and road debris you will be happy it was so cheap and generic, at which point you will know the final size and quality of the intercooler you will need.

For example say you decide to surpass 600rwhp and install a larger turbo after a couple years and notice the IAT is rising where it did not used to rise as much. Now you understand that the intercooler is just barely cutting it, so you toss the cheapy $100 unit and install something slightly larger and more quality. And take measures to protect it from debris in the process.

On the other hand say you are happy with 600rwhp and the current IAT is reasonable. You can still toss the cheapy generic $100 intercooler and install something fancier, quality, perhaps even smaller.

The idea here is to MINIMIZE the size of the intercooler as much as possible (quality over quantity). While at the same time SAVE MONEY by using generic, cheap units, to learn with. There may be some fabrication, some moving around of the unit, higher or lower, covered or uncovered, air dams, position angle, etc... to adjust before you realize and finalize the exact size and quality of the intercooler.

Pressure supplied by compressor pump is initially kinetic energy which is converted to pressure (paraphrasing from the fluid mechanics book). There are losses due to friction along any length of pipe, so care must be taken to minimize pipe length, and that includes intercoolers (they are just large 'pipes' causing friction and lost pressure). Therefore, intercoolers and pipes causing pressure drop, will reduce engine output (Intercoolers REDUCE engine power due to lost kinetic energy from friction). That is why we wish to minimize the pipe length and intercooler volumes, it will minimize friction, give max boost 'response' and maintain more kinetic energy and overall produce more power.

Just to be clear, most turbochargers for V8 engines can easily overcome the losses of pipe and intercoolers. It isn't as important as say, a 2L engine with a small turbo, to minimize the intercooler volume. So my general advice, using generic intercoolers, for V8 engines is to use the largest intercooler you can fit and not worry about minimizing the intercooler volume. It would go something like this:
1. measure the max size intercooler you can fit and buy the largest unit (generic, cheap)
2. Install and test the unit, move it, angle it, duct work it, create protection for it, all the while beating it from regular driving
3. finalize the installation and use the data you've collected to determine if the intercooler needs to be larger, or could be smaller
4. Finally, buy the more exact, quality intercooler your car deserves, toss the cheapy, and verify that it suits your needs

In general we need to empirically (experimentally) determine what intercooler will 'work' and which is sufficient. You can perform calcs all day but the real world situation, pipe volumes and lengths, turbo selection, ambient temps, engine use, underhood temps, fan situation, airflow duct work, etc... its too many variables to calculate an exact size needed. You must install and test a (cheap, generic) unit is the ideal learning curve to start you off and go from there as you collect data (IAT and response data) you can determine what the setup 'is asking for'