For you turbo gl10 guru's

[pwoens]

I keep hearing the "downpipe" being talked about?? Is the downpipe the exhaust pipe that has the "turbo style catalytic converter" or whatever its called, in it??? I keep hearing about cleaning the downpipe and cutting the bottom of the airbox out?? Should I do any of this??

 

Also can I remove my air filter box and put in a k&n cone?? I have all that electrical "stuff" on the pipe running from my air box to the turbo "stuff" and assume the car needs this to run properly?? Should I just leave it alone if its working good??

[Flowmastered87GL]

Depends...

 

If you drive in a dusty area I would suggest keeping the airbox stock. If you do mostly city driving by all means cut out the bottom or swap to a universal cone type air filter.

 

As for removing the cat in the downpipe after the turbo... Technically it IS illegal so if it comes time to sell it I wouldnt go bragging that the pipe is hollow. Some people have ethical issues with removing the cat. Personally I dont, but some people see it as more pollution for very little performance gain. Its your choice though.

[All_talk]

Depends...

 

If you drive in a dusty area I would suggest keeping the airbox stock. If you do mostly city driving by all means cut out the bottom or swap to a universal cone type air filter.

Keep in mind if you do this you will now be drawing warmer air from within the engine compartment, not the cooler air from in the fender well.

 

Just about every car since the early ’80 has had the intake routed in front of the core support or into the fender well to pick up unheated air, I always get a kick out of the after market “cold air intakes” that put a cone filter under the hood.

 

 

Not that the stock air box isn’t restrictive, but why do a performance mod that only goes half way and negates most if not all of the gain.

 

 

Gary

[baccaruda]

here's the skinny on the filter mod:

 

cone / K&N style filters flow more but filter less. their flow gain is greater than their filter loss but they still have filter loss.

the stock airbox, with the bottom cut out, is in perfect position to receive cooler air from under the car. someone (maybe skip) tested this a while back but (i think) people are preoccupied with how cool the cone filters look and most don't bother to properly insulate THEM against hot engine air either.

Both mods are drastic improvements for a turbo car. Driving west up Vantage on I-90 it let me go 90+ in 5th gear when before, on an earlier trip, in the same car, i was topped out around 50 in 4th gear.

I'd say that if you have a mostly stock engine (i.e. you're not going all the way with a performance build) then what's the point of maximizing flow potential that will rarely if ever be necessary?

 

The crossover pipe or up-pipe is the one that wraps around under the front of the engine and receives from both of the heads, and feeds the turbo from underneath. the downpipe is the one that comes off of the turbo and has the two converters (first is oxidizing, second is reducing) on it. having no catalytic converters will make the car more fun to drive but who knows what will happen when it's emissions time?

[stngllhm]

move to wyoming there are no emisions. i have 2 1/2 exhaust from the turbo back. i was thinking about having a new up-pipe made any ideas

[NorthWet]

*edit*: I'd forgotten the title said "guru" when I wrote this. I do not qualify, but still think my comments are relevant.*end edit*

 

I'm going to write a rant on this later, but for now I will mostly agree with All_talk.

 

If you cut up your airbox you will increase the noise (I have an aversion to listen to a loud monotonic drone for 15-16 hours straight, but that is just me) and you will not be doing your engine any real good. Seems to me that improving the airbox and using a standardized filtration medium (replaceable at any walmart/napa/csk/whatever) makes more sense than drawing hot air though an overpriced cone. Again, personal preference, possibly influenced by the onset of old-timer's syndrome.

 

As far as catalytic converters, I am against the continued practice of dumping what has become mature emissions control equipment. Instead of completely removing effective equipment, why not just bring it up to the New Millenium? Get a free-flowing 3-way catalyst to replace the 2 old-tech and cost-conscious cats. Better flow, probably better emission reduction, and the birds won't be croaking as you drive by.

 

But of course maybe people enjoy their fancy fast cars smelling like a '60's pickup truck.

 

Sorry, spent more than my alloted 2 cents.

[stngllhm]

hey cats cost a lot of money i don't have so i work to get as much power with as little cost as possible.

[Danbob99]

ohy, no kidding, run a price check on the price of the 3-way high flow cats, and a pricing on the hollowing of a cat, if your poor, like me, i'd certintly opt for the free way. Though i do still run both cats on my wagon, no muffler, i'd like to change it one day. The cost of having the custom pipe bent for my exaust is going to be a large bill to start with, not counting the cost of what it would be if i wanted to run it with high flow cats.

 

Now...i'm not saying every one should run w/o cats, if you have the extra money, by all means, go and buy those super cool hi flow cats, save a few trees and birds.

 

On the intake, i've not had many problems with the cone that i have in the engine bay, it would be a great idea though to route that cone filter into the wheel well, where the stock one pulled from..i wonder if there is room for a full filter in there after pulling out the original air piece thats in there? time for a run to home depot

[calebz]

Guys.. its called pay to play... If you want such a performer, shell out the cash and do it right.

 

If you cut up your airbox you will increase the noise (I have an aversion to listen to a loud monotonic drone for 15-16 hours straight, but that is just me) and you will not be doing your engine any real good. .

I disagree with this however. Having run stock, cut out and cone filter, I will say that as a free mod, the cutout is the way to go. Definite increase in highend power availability. Continues to pull past 6k, whereas before that just wasn't an option.

[pwoens]

Well, I basically got a APC cone filter brand new for free. So I am in the process of either making a fiberglass MAF mount or ??? BUT, I am considering cutting and fabbing the existing hole in the fender well for the air box to be bigger and accomodate the cone filter. If nothing else this will atleast alleviate some of the engine compartment heat??

 

Maybe the cut is a bad idea because I have not heard of any one doing this?? Opinions??

[Myxalplyx]

My two cents!

 

I don't own any 1.8ltr turbo's but two XT6s. On one of the XT6s, I tested the stock intake vs stock intake with snorkus cut out and routed to my front foglight vs intake piping and cone filter drawing air from the HOT engine bay.

 

Stock air box with a stock air filter would run in 16.6s-16.7's @77-79mph.

 

Stock air box with stock filter (or no air filter, same results) and snorkus cut and routed out to the foglight produced 16.5-16.6s @81mph. Highway passes had leaner air/fuel ratios than stock and car didn't need to downshift to get it moving as it did previously at certain mph points.

 

3" piping to maf to K&N cone filter produced 16.4s @ 82-83mph (Mostly 82mph). If the cone filter was surrounded with cardboard, with only an opening on the snorkel part, I had gotten 83mph. Despite the really hot temperatures underhood, the car still ran faster than it did with the stock air box and snorkus routed to the passenger fog light.

 

Mind you, I tested with the stock airbox on 87 octane and 89 octane with the 3" piping to avoid detonation/pinging. I just wanted to point out that even though your car may be pulling in HOT underhood heat, it doesn't necessarily mean it's going to run slower or poorly. I used to believe this as well. I'm guessing the better airflow through the K&N air filter and 3" piping more than offsetted the hot air being pulled in so much so that it performed better than the stock airbox (even with the snorkus modified) pulling cooler air.

 

 

Foglight, snorkus cutout, 2.5" piping to Maf to 3" piping to 2.75" throttle body(stock) will be tested next when breaks are fixed. The intake setup is done.

[rallyruss]

currently I have a subspeed down pipe 3 way cat 2 1/2 pipe out the rear. stock up pipe.

 

this part ofthe set up works really well.

 

I used to run a guted down pipe with an exta waste gate pipe added into a 2 1/2 system out the back. I only used this for rallyX but it ran well. now its just sitting on the side of the house.

 

as for intake I feel I have found the best of both worlds. I use a K/N drop in filter(not a cone) and have removed the intake silencer in the fender as well as enlarging the opening from the fender into the air box.

 

I also run an intercooler.

 

the good part about my set up is that it runs a lot stronger than a stock set up but looks rather stock and is clean.

the bad part is that it has surpassed the tiny stock turbos flow ability and It now tends to overboost at high RPM.

 

thus the need to get my TD04 installed.

 

you can do cheap mods no problem but if you really want it to go fast AND be durable you need to save you cash and do it right.

 

of course the search function will bring up many previous discussions about the mods in question.

 

good luck and happy tuning.

[NorthWet]

Thanks, rallyruss. I like that approach to performance mods. I was thinking about going with a larger airbox (with correspondingly larger filter) and rerouting the air intake... not sure if through an enlarged fender opening or perhaps forward to cool air.

 

Decent flowing 3-way cats aren't that expensive (at least not when one then talks about buying custom up/down pipes and aluminum fart-boxes).

 

Question about the typical filter cone: Are these regular filter-paper or are they the oiled gauze type? If paper-type (similar material to stock), then they get trashed if they get wet/moist.

[rallyruss]

.

 

Question about the typical filter cone: Are these regular filter-paper or are they the oiled gauze type? If paper-type (similar material to stock), then they get trashed if they get wet/moist.

normaly they are a oil soaked gauze material such as K/N or a foam type. personaly I lean twards the K/N type. I have seen motors lost due to crapy foam filters. This does not mean all foam filters are junk but I cannot tell the junk from the good ones yet.

[Myxalplyx]

the good part about my set up is that it runs a lot stronger than a stock set up but looks rather stock and is clean.

the bad part is that it has surpassed the tiny stock turbos flow ability and It now tends to overboost at high RPM.

I'm assuming you are running more than the stock boost (7psi or so) on your setup to be running out of flow ability. Is this right?

 

Being ignorant, I'd normally assume you are running out of flow ability with the intake and exhaust mods at stock boost. Is this what you meant?

[NorthWet]

normaly they are a oil soaked gauze material such as K/N or a foam type.

Back in the '70s and '80s, K&Ns were popular amongst us murdercyclists on our Japanese 4-cylinders. Oiled gauze led to a lot of early rebuilds. We geniuses (geniux?) also replaced our fair-sized, common filter in a plenum with 4 individual smallish cones. But it was obvious to us that our engines made more power 'cuz we could hear them doing it! But really, seat-of-the-pants is no substitute for real engineering. And there is a reason why car manufacturers use paper filters. And only part of it is cuz they're cheap. I'm pretty sure that Porsche and Mercedes use paper filters.

[torxxx]

Well, I basically got a APC cone filter brand new for free. So I am in the process of either making a fiberglass MAF mount or ??? BUT, I am considering cutting and fabbing the existing hole in the fender well for the air box to be bigger and accomodate the cone filter. If nothing else this will atleast alleviate some of the engine compartment heat??

 

Maybe the cut is a bad idea because I have not heard of any one doing this?? Opinions??

I Am currently trying to figure out how to rig up a hood scoop and plumbing to get cold air from the hood into the intake. I just need to figure out what kind of pre filter I need from the hoodscoop to keep water and crap out of the air intake.

 

I ran my car with a k&n cone filter for 6 months and I ended up putting the stock SPFI air intake and filter back on it. All the mudding I did this fall, I was cleanin that k&n like once a week

[rallyruss]

I'm assuming you are running more than the stock boost (7psi or so) on your setup to be running out of flow ability. Is this right?

 

Being ignorant, I'd normally assume you are running out of flow ability with the intake and exhaust mods at stock boost. Is this what you meant?

it is set at stock boost level yes but the combination of flow increasing mods makes it flow more than it was designed for. the wase gate opens to dump and limit boost but the opening is rater small and enough flow is still forced thru the turbo to keep boost climbing after it has tried to limit it. this usually happens under a good full throttle load at 4500 rpm or higher.

we had a discussion on this a while back where others had noticed the same thing after doing some good intake and exhaust mods.

if you compare a stock turbo next to say a TD04 you can really see the difference in wastegates.

 

northwet- I respect your opinions on the K/N type filters but I personally have never seen any ill effects from running one. I have been using them for the last 10 years on multiple vehicles. I do agree that a GOOD paper element filter is a verry trustworthy filter. I have seen crapy ones fail and cause problems espically if water is added to the situation. I only have one car running a paper element now and thats my new(to me) turbodiesel mercedes. the stock filters in those cars are awesome.

most japan designed vehicles dont use paper element any more but rather a synthetic material thats a bit more open and breathable. so I guess its a matter of personal choice as there are benifits and drawbacks to all designs.

[Myxalplyx]

it is set at stock boost level yes but the combination of flow increasing mods makes it flow more than it was designed for. the wase gate opens to dump and limit boost but the opening is rater small and enough flow is still forced thru the turbo to keep boost climbing after it has tried to limit it. this usually happens under a good full throttle load at 4500 rpm or higher.

we had a discussion on this a while back where others had noticed the same thing after doing some good intake and exhaust mods.

if you compare a stock turbo next to say a TD04 you can really see the difference in wastegates

Wow! This is interesting. I don't mean to beat on a dead horse but I didn't realize that increasing the airflow with the exhaust/intake would override the wastegate's 'purging' ability. I guess this is the same problem some of the WRX folks have when they get some aftermarket intakes and run lean. I just never really thought twice about it. Wouldn't a 'better' wastegate and BOV remedy the situation? I already know more fuel would take care of it but just curious. Thanks!

[NorthWet]

I Am currently trying to figure out how to rig up a hood scoop and plumbing to get cold air from the hood into the intake. I just need to figure out what kind of pre filter I need from the hoodscoop to keep water and crap out of the air intake.

A thought... Anybody done, or seriously thought about, tapping into the base-of-windscreen ventilation plenum to get cold air? Still would have to do a little something to deal with the "water and crap" issue, but prob less so than with a scoop. You also get a minor benefit in that the window base area is a high pressure area. Benefit for old-fogeys is that it wouldn't need to look mod'ed.

[pwoens]

A thought... Anybody done, or seriously thought about, tapping into the base-of-windscreen ventilation plenum to get cold air? Still would have to do a little something to deal with the "water and crap" issue, but prob less so than with a scoop. You also get a minor benefit in that the window base area is a high pressure area. Benefit for old-fogeys is that it wouldn't need to look mod'ed.

Something that comes to mind with this idea is putting the car in a wind tunnel. The flow of air goes over the hood and up the windshield. It would almost suck the air out of the air box instead of forcing air into the air box??? MAYBE??? :-\

[rallyruss]

Wow! This is interesting. I don't mean to beat on a dead horse but I didn't realize that increasing the airflow with the exhaust/intake would override the wastegate's 'purging' ability. I guess this is the same problem some of the WRX folks have when they get some aftermarket intakes and run lean. I just never really thought twice about it. Wouldn't a 'better' wastegate and BOV remedy the situation? I already know more fuel would take care of it but just curious. Thanks!

fourtunately it does not run lean. it would be a bandaid to just put on an extra bypass valve and the bov has nothing to do with boost regulation while you are on the gas.

so the best solution I see is the TD04 that is actually better matched to the EA82T. if the bidding goes well I will have an intercooler today to complete the system.

 

now back to air filters. the fender is probaby still the best location for a good cold air intake. air thru the hood means water too. this brings somthing to mind oh yeah hydralock.

[oddcomp]

what northwet is talking about is cowl induction it works well with the ride setup the low pressure are a at the base of the windowwill force air into what ever it can..

go take apeek at the factory camaro and other version of cowl induction

with the "reverse" scoop used for it it also keeps the water and junk away from the filter usually

 

now if someone had the time "wish i did" to fab u[ a fiberglass intercooler scoop and then behind it also a cowl induction setup for the air filter that would be a good setup

 

if i can find the time and money i will do that plus add extra fiberglass material so i can put my boost gauge and other need to know info up there i nmy line of sight

 

btw search for like cowl induction theory or operation

or you can borrow some of the "old school" books i have

[rallyruss]

what northwet is talking about is cowl induction it works well with the ride setup the low pressure are a at the base of the windowwill force air into what ever it can..

go take apeek at the factory camaro and other version of cowl induction

with the "reverse" scoop used for it it also keeps the water and junk away from the filter usually

 

now if someone had the time "wish i did" to fab u[ a fiberglass intercooler scoop and then behind it also a cowl induction setup for the air filter that would be a good setup

 

if i can find the time and money i will do that plus add extra fiberglass material so i can put my boost gauge and other need to know info up there i nmy line of sight

 

btw search for like cowl induction theory or operation

or you can borrow some of the "old school" books i have

you are correct. but the old camaros with cowl induction also had many motors fail due to water intake and then hydralock. I understand the principle in question I just want to point out that you would have to get it done just right or you may have a serious problem during the rainy season or serious puddle smashing.

[NorthWet]

Yeah, oddcomp, my thought was basically cowl induction, but a little less in-your-face (almost literally!) than what GM did. And I think that rallyruss' comment about trying to breathe water would also apply to a regular hood scoop or any other system open to weather. Definitely needs to be thought through to deal with water/debris, otherwise could do way more harm than good. And yeah, my bias is towards hard surfaces (I prefer lower over lift), so I don't often think about how to not suck mud into my engine. If I planned to go mudding, I would definitely use a K&N plus anything that would keep me getting mostly air.

 

pwoens: changes of airflow cause either a positive or negative pressure, with a relative restriction (such as putting a windshield into the flow path coming off of the hood) causing the junction (between hood and windshield) to experience a positive pressure. Ventilation intakes take advantage of this. It is generally not much except at very high speed, but it is there. And drawing this air off helps reduce drag, but again not by much.