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Old 12-06-2017, 05:04 PM   #1
Zanna-K
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Default Deleting TGV while keeping EGR?

My understanding of how EGR and the TGV's work together is limited, but I would like to retain the EGR system for the improved fuel economy and emissions control while deleting the TGV system to remove restrictions from the intake system.

Is this something that's even doable with the 2015+ WRX or is the TGV required in some way for the EGR system to function correctly?
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Old 12-06-2017, 07:52 PM   #2
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Iíve had this done for about 6k miles now. I get a slight stumble on partial throttle between 1500 and 2000 rpm while cruising. Unplugging the egr is an option but the slight stumble isnít really an issue as Iím rarely in the condition to cause it. To my understanding it wonít cause any damage, just an annoyance.
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Old 12-06-2017, 10:53 PM   #3
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Originally Posted by SoFlaRRRex View Post
Iíve had this done for about 6k miles now. I get a slight stumble on partial throttle between 1500 and 2000 rpm while cruising. Unplugging the egr is an option but the slight stumble isnít really an issue as Iím rarely in the condition to cause it. To my understanding it wonít cause any damage, just an annoyance.
Hm, and that's not something that can be tuned out huh?
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Old 12-06-2017, 11:58 PM   #4
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I wouldn't do it. My understanding is that the TGV and EGR work together and should be left alone, or both deleted. I would assume deleting only 1 would complicate things for your tuner.

The TGV "tumbles" the air to allow better mixing of the air/fuel. This is important when you have an EGR system, because at partial throttle a percentage of your combustion chamber is gas that is not combustible. This gas is ment to just take up space to have the engine act as if it was a smaller displacement engine for better fuel economy. If you delete the TGV but keep the EGR system, you no longer have the same air/fuel mixing, and combustion is a lot less predictable.

If gas mileage and emissions are a concern, I would just leave the car stock.

Disclaimer: Everything above is from internet research, I'm no expert and have had a few beers.
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Old 12-07-2017, 07:44 AM   #5
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...Everything above is from internet research, I'm no expert and have had a few beers.
This basically makes you an expert and ultimately liable... LoL 😂
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Old 12-07-2017, 07:47 AM   #6
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Quote:
Originally Posted by Zanna-K View Post
My understanding of how EGR and the TGV's work together is limited, but I would like to retain the EGR system for the improved fuel economy and emissions control while deleting the TGV system to remove restrictions from the intake system.

Is this something that's even doable with the 2015+ WRX or is the TGV required in some way for the EGR system to function correctly?
I can understand removing EGR and leaving TGV. But not the other way around. The TGV's are there to properly mix the air/EGR and for a lean burn that tumbling air is just as important as the EGR itself.
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Old 12-07-2017, 08:05 AM   #7
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Quote:
Originally Posted by Comikazi View Post
I wouldn't do it. My understanding is that the TGV and EGR work together and should be left alone, or both deleted. I would assume deleting only 1 would complicate things for your tuner.

The TGV "tumbles" the air to allow better mixing of the air/fuel. This is important when you have an EGR system, because at partial throttle a percentage of your combustion chamber is gas that is not combustible. This gas is ment to just take up space to have the engine act as if it was a smaller displacement engine for better fuel economy. If you delete the TGV but keep the EGR system, you no longer have the same air/fuel mixing, and combustion is a lot less predictable.

If gas mileage and emissions are a concern, I would just leave the car stock.

Disclaimer: Everything above is from internet research, I'm no expert and have had a few beers.
I came here to say exactly all of this.
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Old 12-07-2017, 10:03 AM   #8
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I originally wondered whether deleting only the TGV was possible because the 2015+ WRX has no port injection (which is what I thought TGV's were for) and I had read that the TGV's just stay fully open a few moments after start-up.

I hadn't really thought about how inert exhaust gases from the EGR system would still affect air/fuel mixing even in an engine with Direct Injection, but now that you guys mention it, that does make sense.

Have any of you guys done the EGR/TGV delete and taken stock of the difference in mpg? If it's 1 or maybe even 2mpg then perhaps I'll just go the full EGR/TGV delete route but if we're talking like 4, 5mpg then we're down to STI levels of gas-guzzling and one of the reasons I went with the WRX was for improved fuel economy of the FA20DIT. If that were the case, I'll just leave well enough along and stick with TMIC, Charge Pipe, and dry flow drop-in filter as the only intake modifications.
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Old 12-07-2017, 11:10 AM   #9
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Quote:
Originally Posted by Zanna-K View Post
I originally wondered whether deleting only the TGV was possible because the 2015+ WRX has no port injection (which is what I thought TGV's were for) and I had read that the TGV's just stay fully open a few moments after start-up.

I hadn't really thought about how inert exhaust gases from the EGR system would still affect air/fuel mixing even in an engine with Direct Injection, but now that you guys mention it, that does make sense.

Have any of you guys done the EGR/TGV delete and taken stock of the difference in mpg? If it's 1 or maybe even 2mpg then perhaps I'll just go the full EGR/TGV delete route but if we're talking like 4, 5mpg then we're down to STI levels of gas-guzzling and one of the reasons I went with the WRX was for improved fuel economy of the FA20DIT. If that were the case, I'll just leave well enough along and stick with TMIC, Charge Pipe, and dry flow drop-in filter as the only intake modifications.
MPG is completely dependent on your right foot. From completely stock to full bolt ons i've noticed a decrease in mpg of maybe 5mpg, but thats more attributed to me wanting to hear my turbo spool, exhaust afterfire, and whooshing noises and feel the power push me into my seat than it is because a few parts were changed and then tuned.
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Old 12-07-2017, 12:48 PM   #10
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Originally Posted by alapilusa View Post
MPG is completely dependent on your right foot. From completely stock to full bolt ons i've noticed a decrease in mpg of maybe 5mpg, but thats more attributed to me wanting to hear my turbo spool, exhaust afterfire, and whooshing noises and feel the power push me into my seat than it is because a few parts were changed and then tuned.
That's true, of course - it's hard not to be a hooligan in the WRX sometimes, even stock.

More specifically, though, I was wondering about how the EGR system itself affects fuel consumption. EGR effectively reduces engine displacement by partially filling up the cylinder with an inert gas that cannot combust again, so if the FA effectively becomes something like a 1.6L (making up numbers for the sake of argument) engine while EGR is on at cruising speeds does that actually save you a ton of mpg?
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Old 12-07-2017, 01:32 PM   #11
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Quote:
Originally Posted by Zanna-K View Post
.....I had read that the TGV's just stay fully open a few moments after start-up.
I believe that even when fully open, the TGV's will still have a tumbling affect on the air, because the "flapper valve" (whatever it's called) is still physically there.

Quote:
Originally Posted by Zanna-K View Post
Have any of you guys done the EGR/TGV delete and taken stock of the difference in mpg?
I haven't done them yet, I am planning on doing TGV and EGR deletes in a month or 2. But I have read many comments from people on this forum who have done it, and they all seem to say the loss in fuel economy is very minor.

But I think you are focusing on the wrong reasons. The pros and cons to an EGR/TGV delete are:

+ Reduced intake air temperatures
+ Reduced deposits on intake valves
+ Better partial throttle power

- Increased combustion chamber temperatures
- Worse fuel economy (most people seem to say it is only a slight drop)
- Worse emissions

TGV/EGR deletes aren't really done for full throttle power. If that's what you care about I would do other mods (J-pipe, TMIC, flex fuel, charge pipe etc.)

But you seem to really care about gas mileage, so I wouldn't touch TGV's or EGR.

Also, I think ericdet brought up a good point. Deleting only the EGR should be fine, but don't delete only the TGV's.
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Old 12-07-2017, 01:51 PM   #12
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So here is how my fuel economy has been effected.
2015 - Mostly stock average recorded fuel economy = 24.76mpg
2016 - Stage 1 (intake, tune) 18 wheels and 255/40 summer tires average fuel economy = 23.52mpg
2017 - Stage 2 (intake, j pipe, tgv/egr delete, intercooler, tune) 18 wheels and 255/40 summer tires, added sti wing average fuel economy = 22.4 mpg

Last edited by 10secdream; 12-07-2017 at 02:00 PM.
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Old 12-07-2017, 02:07 PM   #13
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Deleting the EGR also helps prevent a lot of the carbon buildup in your intake valves and lowers your intake temp, which in the long run will save you money and headaches. Simply unplug the EGR plug under the intercooler/manifold, get a retune ($50 to $100 depending on your tuner) specifically for the egr delete in case you do not like the loss of mpg. I lost about 3 to 4 avg mpg from the egr unplug.
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Old 12-07-2017, 05:16 PM   #14
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Quote:
Originally Posted by Zanna-K View Post
I originally wondered whether deleting only the TGV was possible because the 2015+ WRX has no port injection (which is what I thought TGV's were for) and I had read that the TGV's just stay fully open a few moments after start-up.

I hadn't really thought about how inert exhaust gases from the EGR system would still affect air/fuel mixing even in an engine with Direct Injection, but now that you guys mention it, that does make sense.

Have any of you guys done the EGR/TGV delete and taken stock of the difference in mpg? If it's 1 or maybe even 2mpg then perhaps I'll just go the full EGR/TGV delete route but if we're talking like 4, 5mpg then we're down to STI levels of gas-guzzling and one of the reasons I went with the WRX was for improved fuel economy of the FA20DIT. If that were the case, I'll just leave well enough along and stick with TMIC, Charge Pipe, and dry flow drop-in filter as the only intake modifications.
While TGV's on the EJ in the past have been barely functional, that is not the case on the FA. The TGV's are constantly opening and closing unless your tuner has disabled their function. Cobb OTS maps as well as the factory Subaru maps have TGV closed until 58 g/s airflow. Anything below this your TGV's are closed. Anything above they are open. You can monitor TGV position on the AP. They do open at certain angles depending on the RPM.

TGV's do rob some VE from the engine. Deleting them will increase airflow and power at all the RPM's you care about anyway. I personally view TGV's as a latter piece of the puzzle. A J-pipe and flex fuel are much larger performance differences mod for mod.
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Old 12-07-2017, 05:58 PM   #15
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Quote:
Originally Posted by 10secdream View Post
So here is how my fuel economy has been effected.
2015 - Mostly stock average recorded fuel economy = 24.76mpg
2016 - Stage 1 (intake, tune) 18 wheels and 255/40 summer tires average fuel economy = 23.52mpg
2017 - Stage 2 (intake, j pipe, tgv/egr delete, intercooler, tune) 18 wheels and 255/40 summer tires, added sti wing average fuel economy = 22.4 mpg
wow, thats the kind of MPG id get on my old EJ255. So much for progression in tech
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Old 12-07-2017, 07:17 PM   #16
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Originally Posted by curiousfish View Post
wow, thats the kind of MPG id get on my old EJ255. So much for progression in tech
I mean there are lots of factors but that is my average fuel economy for a entire year and half the year is spent in cold snowy winter months (I live in Canada). I do not drive a ton of highway either on my way to work.

My stage 2 Forester XT for reference averaged 19.9 mpg.
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Old 12-07-2017, 09:23 PM   #17
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My fuel consumption got better after the tgv/egr delete and tune. Most likely the better tune outweighed the tgv/egr delete.

Either delete both or leave them. I do not think you will notice the difference in power between tgv's and tgv delete.

I wanted to delete the egr for reducing the carbon on the intake valves and therefore did the tgv deletes as well as they work together.

Any money on fuel you save by keeping the egr you will spend on walnut blasting to keep your intake valves clean!
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Old 12-08-2017, 12:17 AM   #18
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Delete both at once.
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Old 12-08-2017, 09:51 AM   #19
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The biggest hit in fuel consumption comes with a J-pipe. Less exhaust restriction means the turbo spools up more at the same rpm/throttle/load so you end up losing out on the highway.
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Old 12-09-2017, 05:56 PM   #20
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Quote:
Originally Posted by 10secdream View Post
I mean there are lots of factors but that is my average fuel economy for a entire year and half the year is spent in cold snowy winter months (I live in Canada). I do not drive a ton of highway either on my way to work.

My stage 2 Forester XT for reference averaged 19.9 mpg.
then id say youre getting great gas mileage!
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Old 02-05-2018, 01:37 AM   #21
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First I know this isn't a gas mileage thread but just going off my average MPG's on the mini display I got 27.3 MPG on the stock tune and 27.9 running the Cobb OTS stage 1. That is a premium 2015 WRX. Also as many have said you need to remove your EGR if you are removing your TGV. The form in the link below is a of a guy who learned this trying to tune is own car with a TGV delete. There is a lot of great info in this thread on why and how.
https://forums.nasioc.com/forums/sho....php?t=2743792
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Old 02-05-2018, 06:00 PM   #22
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I got in contact with Bren Tuning the other day asking if they would be able to etune an EGR/TGV delete (i read that e tuning an EGR delete can be a little tricky) and Bren got back to me saying that an EGR delete isnt necessary because it doesnt help much with power or reduce carbon build up, but after reading everything it makes sense to delete both
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Old 02-05-2018, 09:23 PM   #23
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I did TGV deletes and just unplugged the EGR. Tune went great and I don't notice any difference in fuel economy. It could be because the car was tuned a couple times before this last one.
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Old 04-11-2018, 09:46 PM   #24
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Quote:
Originally Posted by subarulz! View Post
I did TGV deletes and just unplugged the EGR. Tune went great and I don't notice any difference in fuel economy. It could be because the car was tuned a couple times before this last one.


DO NOT JUST UNPLUG THE EGR! I drove for one year with the tgv deletes and the egr unplugged. I then got a loud hissing/electric buzzing noise from my engine bay when it warmed up. Also a big drop in power and boost pressure. After performing a smoke test we determined the egr gasket was the weak point causing the vacuum/boost leak at the egr. Just spend the $39.99 for the IAG egr delete kit and save yourself the headaches. Because the egr is unplugged when the valve is closed all of the hot gasses are not recirculated back into the engine causing the gas to try to escape through the egr gasket.



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Old 04-11-2018, 10:32 PM   #25
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^^ excellent feedback to help others avoid the PAIN.

Thanks
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