Engine efficiency issue?

[ChrisW434]

Hi again all,

i got the GTT dyno'd and the car was down on power for what i believe it should be making (very common story i know)...

The power curve is good, with great Lambda readings, and drives well apart from during very low speeds i.e: carparks (seperate thread for that issue).

It has all the usual parts that i reckon are pretty well matched, and in some cases, overkill for my needs (i'm ok with that).

2.5L Neo with supporting mods, manual trans

kelford drop-ins, Performance springs, Ferrea S/S exhaust valves

Hypergear ATR45SS-2 (gtx3582 compare)

6boost, 3.5" exhaust, 60mm plumbback gate

Plazma pro-series cooler, tophalf and 66mm TB.

Haltech elite 2k on E85 , Ross triggers, R35 coils

- Power peaked at 530rwhp on hub dyno at 8k (25psi boost).

The tuner commented on how the engine wouldn't respond with more boost, as if there is a restriction somewhere. Tapped out at that power level....

Couple ideas for what would be choking up the engine would be ;

- Plumbback causing backpressure, got some advice to convert to screamer 

- Valvespring tension incorrect, causing float at 25psi and up. I didn't test and shim the springs, i just installed them with a shim under each one. Perhaps the Ferrea locks are a different height? Torque curve is smooth all the way up, no erratic spikes on the curve, so not sure if its actually floating..

I reckon this setup should make over 600rwhp at peak with this setup..

Thoughts on either option, or another potential issue?

Edited August 17 by ChrisW434

[Kinkstaah]

Here's a result from the man himself. He ran 40psi to make 570kw.

That said, replicating Tao's setup has always been contentious, at best. There's no doubt that car would have been externally gated, and assuming you have the same rear housing size Tao did in the above example, there's not much else that is different other than more boost, and having true external gates.

That said, he is making your target (~450kw) at about 28psi of boost. External gates really do make a difference. If it's viable it's worth testing to see if you get instant results.

I assume you have pretty much an open intake and/or straight pod being dyno'd with the hood up. What's your IAT's like at the end of the glory runs? Tao doesn't have that data but he's always run a pretty maxxed out setup with his turbos being absolutely fully supported in every way.

There's a lot of people upset with HG turbos, because they don't have the same test setup that Tao uses when he showcases the turbos, and their results don't come out the same.

[ChrisW434]

11 hours ago, Kinkstaah said:

Here's a result from the man himself. He ran 40psi to make 570kw.

That said, replicating Tao's setup has always been contentious, at best. There's no doubt that car would have been externally gated, and assuming you have the same rear housing size Tao did in the above example, there's not much else that is different other than more boost, and having true external gates.

That said, he is making your target (~450kw) at about 28psi of boost. External gates really do make a difference. If it's viable it's worth testing to see if you get instant results.

I assume you have pretty much an open intake and/or straight pod being dyno'd with the hood up. What's your IAT's like at the end of the glory runs? Tao doesn't have that data but he's always run a pretty maxxed out setup with his turbos being absolutely fully supported in every way.

There's a lot of people upset with HG turbos, because they don't have the same test setup that Tao uses when he showcases the turbos, and their results don't come out the same.

Yeah , i actually based a few of my choices around Tao's setup. And wanted to see if i could push it that high. I messaged Tao directly and he suggested the screamer makes a big difference. I currently have an external 60mm Turbosmart gate (to allow low boost on p98 if required) And considering that is a lot easier to try than pulling and sending the head away for valvetrain inspection/setup, it would be worth a try. 
And, IATs were good, i cant remember numbers, but it started raising the temps a bit over that 25psi mark supposedly. Though running a good intercooler is key.
 

Also, i made a mistake in my first post, the runs were on a wheel dyno, not a hub dyno as i originally stated (typo) so thats different also...

Edited August 18 by ChrisW434

[Kinkstaah]

I mean, dynos are different all around the globe. I went a little crazy troubleshooting why my setup is different to American setups. Ultimately they aren't.

If Tao did a quarter mile run and you did, compare MPH at the quarter mark line. It's probably very comparable. Screamer pipes and external gates make massive differences in turbo setups when you need to run a lot of boost. It just gets harder to spin the turbine wheel if the pressure in there is massively high.

There's IWG
EWG
EWG with screamer.

I mean depending on whether you plumb your pipe back in, your External Gate may not really be 'external' when you think about it. It's just relocated from the turbo housing.

Certain turbos handle these scenarios better than HG. Plenty of people have had the same setup, then thrown a Borg Warner or a Genuine Garrett on there and found that they have far more efficiency when brutally 'mistreated' in certain scenarios which can result in better results with a turbo swap too.

[Dose Pipe Sutututu]

Take off the timing cover, are all your timing marks correct?

[ChrisW434]

1 hour ago, Dose Pipe Sutututu said:

Take off the timing cover, are all your timing marks correct?

Yes, the markings are correct. I considered that too.

[ChrisW434]

2 hours ago, Kinkstaah said:

I mean, dynos are different all around the globe. I went a little crazy troubleshooting why my setup is different to American setups. Ultimately they aren't.

If Tao did a quarter mile run and you did, compare MPH at the quarter mark line. It's probably very comparable. Screamer pipes and external gates make massive differences in turbo setups when you need to run a lot of boost. It just gets harder to spin the turbine wheel if the pressure in there is massively high.

There's IWG
EWG
EWG with screamer.

I mean depending on whether you plumb your pipe back in, your External Gate may not really be 'external' when you think about it. It's just relocated from the turbo housing.

Certain turbos handle these scenarios better than HG. Plenty of people have had the same setup, then thrown a Borg Warner or a Genuine Garrett on there and found that they have far more efficiency when brutally 'mistreated' in certain scenarios which can result in better results with a turbo swap too.

Yep, the wastegate is just bellow the turbo. I sort of eliminated the EWG setup was the issue as its 2.5" out of wastegate, merging about 700mm later into the 3.5" exhaust down near the trans. 
Tao did explain with E85 and the boost i want to run (30-35psi), changing to a screamer would make a big difference. 

I don't run a wastegate position sensor (like most streetcars) so i can't see in real time what the wastegate is doing, but i'm assuming it would be fully closed when running higher boost, thus taking the screamer setup out of the equation at full boost? Or would it actually crack open and bleed some exhaust out under big power?

 

Edited August 18 by ChrisW434

[GTSBoy]

34 minutes ago, ChrisW434 said:

Or would it actually crack open and bleed some exhaust out under big power?

Well, it can, which is why 4 port solenoids and then ultimately CO2/high pressure gas control exist.

[Kinkstaah]

The easiest way I can explain it (and it's not a good explanation) is that you're creating backpressure. In effect, when you plumb your wastegate in you're effectively running a smaller exhaust than someone who isn't. We'd like to all think that it doesn't or shouldn't make a difference, but merging the pipes *does* make a difference. Even if you merge it waaay back. It just makes less difference.

It will always flow better if the air from the screamer literally never re-enters the exhaust stream. A turbine wheel isn't exactly the most free-flowing of things when you think about it. What you 'want' is JUST enough exhaust flow to spin the turbine wheel up, then EVERY OTHER PIECE OF AIR to absolutely get out of the way of the exhaust stream.

If it were me, I'd talk to a local fabricator and turn your merge into a removable screamer. Try it out and see.

[ChrisW434]

15 minutes ago, GTSBoy said:

Well, it can, which is why 4 port solenoids and then ultimately CO2/high pressure gas control exist.

Yep sweet. The tuner mentioned that was an option

[ChrisW434]

5 minutes ago, Kinkstaah said:

The easiest way I can explain it (and it's not a good explanation) is that you're creating backpressure. In effect, when you plumb your wastegate in you're effectively running a smaller exhaust than someone who isn't. We'd like to all think that it doesn't or shouldn't make a difference, but merging the pipes *does* make a difference. Even if you merge it waaay back. It just makes less difference.

It will always flow better if the air from the screamer literally never re-enters the exhaust stream. A turbine wheel isn't exactly the most free-flowing of things when you think about it. What you 'want' is JUST enough exhaust flow to spin the turbine wheel up, then EVERY OTHER PIECE OF AIR to absolutely get out of the way of the exhaust stream.

If it were me, I'd talk to a local fabricator and turn your merge into a removable screamer. Try it out and see.

Yep i understand and agree. My exhaust is all v-band coupled and in sections, so i'll just make a screamer pipe and get a exhaust blank. I can back-to-back swap as required then 👍🏻 

Sounds like even with decent (merged) exhaust/plumb-back size, it still may still be creating back-pressure at that boost level/exhaust volume level....

That explanation is basically what Tao was saying also

Edited August 18 by ChrisW434

[hypergear]

To get the most out of the car, you will need to external gate it. Plumb back just doesn't work. And even externally gated, by adding an additional cutout pipe to the dump pipe made a huge difference at this power level. Remember the my test car had a 3 inches cutout pipe in the dump working with a 3.5 inches exhaust and two 40mm external gates. 

At a point when you are be able to rise the inlet boost pressure that makes no power gain is usually due to an restriction on the hot side of the turbo setup, that also causes boost pressure to fall up top as greater volume of flow is required maintain boost pressure per crank revolution increases. 

Stock cams shaft was getting pretty maxed towards 450rwkws, it needed alot more boost to gain additional KW at that point. I would put steps 1 cams in if I was doing it all over again.

Dyno makers are annoying, all clamed making the most accurate dynos in the world, and none of them agrees on power/torque/speed formulation, that causes issues on end users.  If roller dyno was used, you probably see a lower figure due to traction and load. If it was on a Dyno dynamic dyno, you would likely be seeing a much lower figure, that is due to formulation of the dyno software.

 

[ChrisW434]

33 minutes ago, hypergear said:

To get the most out of the car, you will need to external gate it. Plumb back just doesn't work. And even externally gated, by adding an additional cutout pipe to the dump pipe made a huge difference at this power level. Remember the my test car had a 3 inches cutout pipe in the dump working with a 3.5 inches exhaust and two 40mm external gates. 

At a point when you are be able to rise the inlet boost pressure that makes no power gain is usually due to an restriction on the hot side of the turbo setup, that also causes boost pressure to fall up top as greater volume of flow is required maintain boost pressure per crank revolution increases. 

Stock cams shaft was getting pretty maxed towards 450rwkws, it needed alot more boost to gain additional KW at that point. I would put steps 1 cams in if I was doing it all over again.

Dyno makers are annoying, all clamed making the most accurate dynos in the world, and none of them agrees on power/torque/speed formulation, that causes issues on end users.  If roller dyno was used, you probably see a lower figure due to traction and load. If it was on a Dyno dynamic dyno, you would likely be seeing a much lower figure, that is due to formulation of the dyno software.

 

Thanks for chiming in Tao, i appreciate it.

Looks like some exhaust mods will be happening shortly, in particular a screamer setup...
I do have Kelford drop-in cams so hopefully it should make better power on less boost once its all sorted.
 

Cheers for the detail in the response also, great service as always.

[Watermouse]

11 hours ago, Kinkstaah said:

f it were me, I'd talk to a local fabricator and turn your merge into a removable screamer. Try it out and see.

Asking everyone,

Considering I might be in a well policed area, would a screamer pipe with (for example) a varex type valve arrangement, be a sound exercise to explore so as to be able to vent to atmosphere then when required, then be able to feed back into the main exhaust at your settings of choice up to 100% recirculating?

would this be too risky and unmanageable to tune correctly?

[Murray_Calavera]

@Watermouse

The exhaust setup your describing isn't street legal. So if you're going down that path, why bother with the cost and complexities of the varex? You could just run the screamer and if you see the fun police, don't drive on boost?

Or if you want to be street legal, you could get a swappable setup v-bands etc, and run the screamer on track and plumbed in on street?

Edited August 18 by Murray_Calavera

[GTSBoy]

Yeah. given that you can't actually use that much power on the street anyway, it seems kinda pointless to set it up to do so.

[Dose Pipe Sutututu]

Do you have photos of how your EWG is plumbed back into your exhaust system?

Also, your goal of that power isn't far fetched.

My car (many moons before the 3rd engine) ran a prototype ATR43SS2 (smaller than yours) with a 100cell cat, and EWG plumbed back after the cat and made 372kW on a Mainline roller dyno.

I can't recall how much timing (might have been about 21 to 22, can check when Lenovo sends me back my laptop) but I did have about 1.65bar through it.

 

[ChrisW434]

1 hour ago, Dose Pipe Sutututu said:

Do you have photos of how your EWG is plumbed back into your exhaust system?

Also, your goal of that power isn't far fetched.

My car (many moons before the 3rd engine) ran a prototype ATR43SS2 (smaller than yours) with a 100cell cat, and EWG plumbed back after the cat and made 372kW on a Mainline roller dyno.

I can't recall how much timing (might have been about 21 to 22, can check when Lenovo sends me back my laptop) but I did have about 1.65bar through it.

 

Thats reassuring to me that there is an issue. I believe my combo would be mid-to-high 600s rwhp when sorted.

Refer pic (second one for context). I paid attention to bends and where it merged and all that. Maybe the engine wants to keep making power but just really dumps more exhaust volume in the exhaust than i expected and backpressure is building. I'll make a screamer for it and also try a dump pipe on the dyno

Edited August 19 by ChrisW434

[Dose Pipe Sutututu]

I reckon screamer and see how you go 

[Watermouse]

Thanks for the replies,

‘Sorry it was a concept I thought of whilst having a drink

cheers