[TSi92]

I guess that this is the question that I am looking for answers on. My quest started when I was mapping out my IC pipes, and realized that even the shortest route would require 5-6' of pipe. At this point I started entertaining the idea of the HMIC with no pipes. Technically, there is a percentage of loss (pressure drop)for every foot of pipe. That is a fact, wheather it is significant or not is up for discussion. The other topic at hand is the spool time. Because another fact is that it will take the turbo longer to charge a long stretch of pipe than a short stretch of pipe, the significants of that lag is what is up on the table. With both of these small factors added together, will that make my project worthwhile. Remember that to reduce a couple of small factors can add up to a noticable differance. It is like weight reductions, you get rid of a little of this and a little of that, next thing you know the car is down 200 - 300 pounds.

I guess all that work is worth for 3 extra hp and turbo spool up 250 rpm's sooner.

 

[V8s_are_slow]

okay i guess personally it looks and sounds like a nice setup. but i would just have to see the setup with the hood. i personally don't think hacking up a hood would look all that great unless maybe it looked something similiar to the corvette race car version. but that's just my personal opinion. no need to flame me on that alright? no one's opinion is the same. later!
scott

 

[jap drifter]

hey 1fastpos: have you ever considered trying the mkiv supra intercoolers and welding two of those jammies together. one guy on here said he was in the process of doing it but i never heard of anything after that. i know one mkiv intercooler is good for 14bs, 16gs, and i even know a guy with a 20g that runs a single one and its a lower 12 sec car. so with two you are looking at some serious cooling. what turbo are you going to run with this hmic anyway. btw, im not sure how the hell you would fit two supra smic into the front of a dsm. i guess if there is a will, a way, and a plasma cutter anything is possible. just a thought if your results arent what you expect.

another question i think i asked before. do you log at all? i think some before and after logs would be interesting to compare the results.

 

[1 fast POS]

TSi92-----I guess all that work is worth for 3 extra hp and turbo spool up 250 rpm's sooner.

TSi92----I have a BR 20G and a big FMIC with 2.5" piping'92 Talon TSi FWD
K&N cut air can, DDP mbc @ 15 psi, 2.5" downpipe 3" custom cat-back with ultraflo muffler, TMO stage 3 ECU
14.49@99 2.4 60ft

I don't know how you do your math to get 3 extra hp and 250 rpm? But one thing that I do know is from looking at your list of mods verses your time slips, please don't hold it against me if I don't take your advise. You say that your BR20g spools faster than a 14B. Then how come I was laying down 13.50s on a 14B with about $200 bucks in my car verses your $3000+= 14.49.

V8s_are_slow----okay i guess personally it looks and sounds like a nice setup. but i would just have to see the setup with the hood. i personally don't think hacking up a hood would look all that great unless maybe it looked something similiar to the corvette race car version. but that's just my personal opinion. no need to flame me on that alright? no one's opinion is the same. later!

Not familiar with the Corvette race hood. Unless your talking about the Calloway vette that needed a nasty vented hood to keep it from flying off at 220 on the salt flats (twin Tubo, this V8 aint slow). If this is the one that you are talking about, then I vaigly remember. As for the butchering that I will be putting on the hood, I have NO body work experience. But I have three hoods and alot of patience, so I get two tries a couple of road tests and if she makes bad numbers then you will see me on my third hoo with a FMIC. The way I look at it is if it doesn't make the car go faster, I don't want any part of it. I'm sure 92TSI feels the same way.

jap drifter----hey 1fastpos: have you ever considered trying the mkiv supra intercoolers and welding two of those jammies together.

I would LOVE to, however I happen to have disassembled and inventoried three TSIs in the past. So I have all this stuff lying around.

jap drifter----what turbo are you going to run with this hmic anyway

Since the 16g that I was last running has issues, the maiden voyage will be 14B powered. I have a perfect 14B minus about 2 hours of port and polish.

jap drifter----i guess if there is a will, a way, and a plasma cutter anything is possible.

These are the basic principles that I have built this car on.

Ohh, sorry no logger, just allot of guages, smelling the exhaust, and checking the plugs. Maybe I will start logging?

 

[TSi92]

That 14.49 was with the stock 14b, stock sidemount and stock rubber pipes. I haven't raced the car with the 20g yet. I just rebuilt the block and it only has about 350 miles on it. I won't race it until I have at least 1000 miles on it. I was being sarcastic when I said you will gain only 3 hp and spool up 250 rpm's sooner, I just think that it's not worth to go through all that work when it is clear that the hp gain will be not that great. I dunno that's just me, but it's your time and money so whatevers... to each their own.

 

[DOHCdave]

That is an asumtion, however I will entertain that, it may be in the ballpark. However reduced pressure drop is only 1 of the possible advantages. Faster spool, faster recovery after the system has been purged in between gears. The more tube or pipe that the turbo has to charge, or recharge in between gears, the more LAG you will have to wait for.

Blah, Ive never noticed lag between shifts on a 20g, and my turbo can fill a foost of piping if less then a ALOT tenth of a seond.

Why? Why do they have to face the windshield to work? You ever think about ram air, it works (somewhat) with forward facing vents. By facing them forward you get the RAM in ram air. I think if they face the winshield heat will slowly trickle out. But if you want air flow in a bad way you have to turn them around and FORCE the air through.

Blah, totally different situations....ever see v8 hood scoops? There a foot off the car. Ever wonder why? Ever wonder why air ducts are at the back off the hood point towards the windshield? Everwonder about cowl hoods? Ill enlighten you grasshopper. The top of the hood becomes an extremely low pressure area. the air passes 8 inches above it, especcially at highway speeds. The low pressure are DRAWS AIR OUT of vents or louvres. Not because heat rises, its being pulled out quite hard. If they face the wrong way, the SLIGHT air moving towards it will force the air trying to get out back in and do next to nothing. high scoops or bust.

???? Maybe less, maybe more????? Has anyone ever owned a car or a truck with one of those little triangle front windows? You know the ones that you can turn around until they actually face the front of the car (pick up trucks, Jetta, vans). As soon as you get any kind of speed with that window venting from the FRONT the wind comes POURING into the car. I'm talking ashtrays getting blown empty, McDonalds bags flying out of the car its making that jet engine sound sssskshkhhhhhhkhhookookoookoook (well you know). That, I think stands as testimony to my forward vent theory.

No low pressure areas on the sides of cars HOMIE


Why is that? I am not disagreeing with you, I am just looking for a reason, to go with an example. Are you sure that wasn't directly related to the aerodynamics of THAT car? I would think that in the fiat family, the winshield and passenger area would break the flow of air before it gets to the rear engine deck (just a thought). I guess that I just can't come up with a better way to force the air through the IC over such a large surface space from the bottom up. For that matter, where does all the air entering through the radiator go, probably out and under the bottom of the car it sure can't go up? [/B][/QUOTE]

Thats why TMIC's are stupid and replaced...they get shit for air flow with out rediulouc sized scoops and they are still inferior.

 

[DOHCdave]

I guess all that work is worth for 3 extra hp and turbo spool up 250 rpm's sooner.

LOL, hes going to lose hp, thats not a arguement, the point is how much? And 250 rpm? No way, maybe 100. Bigger the turbo, less it matter. They fill pipes much faster once they start spinning.

 

[1 fast POS]

DOHC Dave- sorry, but I have to crash for the night. But I promise to discredit your post first thing in the morning. Now don't be late for school tommorrow, there will be a pop quiz.

 

[V8s_are_slow]

although i personally think it would look MUCH better if the louvers face the windshield, i'm wondering how well the air can flow from bottom to top being that the tranny is directly beneath it thus blocking air. but maybe i'd need to see the setup to know for sure on clearance etc. as for the vette i'm talking about, it's the yellow C5 i see all the time on the GT races on speedvision. know what i'm talking about now? that thing (and the hood) looks awesome!!! now if it were me and i were spending all the money on the setup, i'd at least have a body shop or something maybe try and make ya a hood, or even talk over the design you want with them. instead of hacking up some perfectly good hoods. i'm personally not interested in having this setup myself "only" for the reason that i wanna see that nice and polished frontmount on my car. but i would be interested in seeing how this turns out. heck, maybe one day i could get an old junker 1g (as a sleeper) and do the same thing to. guess we'll have to stay tuned huh? wondering about the effects of spool time and the pressure drop etc. hmmmm, just had a thought, what about maybe a sheetmetal ram air intake that scoops air from the bottom, guides it up under the i/c and out the louvers to the top? thus also keeping the downforce in tact? i dunno, just throwing out ideas. laters!
scott

 

[rallsport]

airflow

You need to think about pressures on this system...the top of the hood is typically a very low pressure area so you should be exhausting the cooling air there. The front of the car is a very high pressure area (air striking front of car as you move forward) so you should get your cooling air from there. Air moving from a high pressure area to a low pressure area will promote good flow. You should duct from the front and up through the intercooler and exhaust from the hood (duct or sealed also). If you don't duct the air and don't force it to move through the intercooler your system will be much less efficient. You want to force as much air as possible over the intercooler. I think you could make this a sweet setup if the cooling air is properly used through good ducting. An intercooler can be put anywhere as long as you supply it with a large volume of cooling air by proper duct work.

 

[1 fast POS]

DOHCdave ----Blah, totally different situations....ever see v8 hood scoops? There a foot off the car. Ever wonder why? Ever wonder why air ducts are at the back off the hood point towards the windshield? Everwonder about cowl hoods? Ill enlighten you grasshopper. The top of the hood becomes an extremely low pressure area. the air passes 8 inches above it, especcially at highway speeds. The low pressure are DRAWS AIR OUT of vents or louvres. Not because heat rises, its being pulled out quite hard. If they face the wrong way, the SLIGHT air moving towards it will force the air trying to get out back in and do next to nothing. high scoops or bust.

DOHC Dave--- You have the exactly correct answer, to the wrong question. If I where searching for a high pressure location for ram air you would be right on, but I am NOT.
First off V8 hood scoops stick up 8inches because of 8" long intake runners/ 6" of carberator/ and 6" velocity stacks with a 4" air filter on top. With two feet worth of crap piled on top of there engines they need more hood clearence, hence foot tall scoops. (but there is truth to the Ram Air reason that they do this aswell)
However there is truth to your high pressure low pressure arguement on your post. I will straighten that out for you I am sure that the article you read in road and track didn't elaborate so I will fill you in. The very front of the car IS the high pressure zone, why? Because as the car is plowing through the air the air slams into the front and gets stacked up. This stacked up air looses speed & volume and gains PRESSURE. The overflow air that rolls off of that stagnent pile of air on the front of the vehicle rolls off and into the high speed air stream. As this high volume high speed air stream starts to travel up the hood it gains VELOCITY. Air with high velocity has LOW pressure (we should know these things considering that it is the very principle in which a turbo exsists). The air does not travel 8" above the hood (LOL). In fact the air that is traveling across the top of the hood has way more speed than the actual vehicles speed.
By the way I can back my info up with a illustration, from a book about ram air, please visit this link and view my latest photo.http://community.webshots.com/user/1_fast_pos
As I had previously stated in an earlier post, with the window venting the air into the vehicle.

No low pressure areas on the sides of cars HOMIE

Well homie says there is low pressure high velocity air on the sides of cars, it is the overflow air that rolls off of the front of the car and the windshield, that rejoins the high speed air stream. This is why when you crack the window a couple of inches it sucks (cigarette ashes and what not) out. However as I last stated in a rescent post, if you redirect that air IN, you get a very high speed, high volumes of air flow. Vents that face backwards on a hood create a rescess, the high speed air passing over this recess draws air out. If you turn the vent around you will be redirecting this high speed air where you want it, in at extremely high volume and speed.
Bottom line, DOHC dave , although your efforts are misdirected you have given me more confidence in this project. Because high velocity/ high volume will cool more efficiently than air at high pressure/low volume. This is why a fan like in your house, or your rad fan,(designed for cooling, as we know) puts out high volumes of air at high velocity.So bottom line is for "Ram Air" high pressure low speed air, you need to place a vent in the front of a vehicle. However for high speed/ high volumes of air, you will find that on top of the hood (better conditions for cooling cooling something).

Thats why TMIC's are stupid and replaced...they get shit for air flow with out rediulouc sized scoops and they are still inferior.

<<Opinion, not fact. So the reasoning still stands, that TMIC are replaced because they are more easily located in the front of the vehicle....

 

[OWGTI]

Here... Look at this....

Yeah I know its an RX-7, but they have SIMILAR body lines, 2 door hatchback.... low hood, low mounted air intake, similar width, height, and length.....

Now, as the air flows over the hood of the car, it's loses pressure, but when it reaches the windscreen, it again comes up against a barrier, and briefly reaches a higher pressure. The lower pressure area above the hood of the car creates a small lifting force that acts upon the area of the hood (Sort of like trying to suck the hood off the car). The higher pressure area in front of the windscreen creates a small (or not so small) downforce. This is akin to pressing down on the windshield.


Hence, this is why the following things work....
Hood louvers that point backward work because look where they are positioned, on the front and middle of the hood but if you look closely, usually they are not placed within the last 8-10 inches of the hood.
Cowl hood scoops that have the onening to the rear work to supply the engine with fresh air because the opening is in a high pressure area of air dammed up along the windshied. So fresh air is being forced in.
NASCAR hood scoops. Nascar vehciles need to maintain a "stockish" appearance so big goofy scoops are out of the question. They use a duct right by the windsheild to feed air to the engine, a hidden cowl hood of sorts. Also the same theory that heater vents on cars use to get fresh air into the cabin.... you know those slots on the rear of the hood that feed air into the vent system......

Locate the louvers as rear facing in the "lift" area of the hood. Hope you brought your pennies cause unless you can find a diagram like the RX-7 for a DSM, you need to go hit a wind tunnel.


Because of the way the engine sits in a DSM (kinda close to the front of the hood) and the position of your IC, it would be nearly impossible to get a vent in the "high" pressure area of the hood. You need a reversed vent in the low pressure part of the hood, extracting the air out from underneath the car. Then you need some ducting from a foglight hole or something to the underside of the IC.

Who's right now, homey (DOCHDave and I are )

 

[OWGTI]

The reason an RX-7 and a Subaru can use a TMIC is because of the way the engines are designed. Have you ever looked at a WRX or a RX-7 Turbo2? If you had, you would know that the engines are very LOW and far back under the hood. Heck the water pump on my RX-7 barely comes to the shock towers, there is room for a whole 'nother rotary engine ahead of it. Anyways, this low, far mounted back engine allows the hood scoop to face forward because the IC is mounted in the back of the engine bay, not the middle like yours is. RX-7s and WRX's can get away with this because they, like I said, mount the IC farther back. You could pull off a TMIC witha front facing scoop if you mounted it where the wipers used to be Well not that far back but you get my idea. Same goes for SVO Mustangs.... Front facing scoop but its in the rear 2/3 of the hood, not the front like you have to/need to/want to do.

 

[1 fast POS]

OWGTI & DOHCDave-- Your information is the solid argument that I would need to change my design. With this new argument on the table it is clearly not in my best interest to persue this design, my only option to help this unit breath mounted against the hood would be to vent from the bottom through the top. I don't feel that this will supply the IC with the volume of air that I would like. So looks like my efforts will be directed to a clean front mount with as short of pipes as possible. I was kind of looking forward to hacking up my hood. Oh well. OWGTI & DOHCDave, either one of you guys needs a Gen 1 hood, let me know.

 

[OWGTI]

Im just glad I could help... It was a real good idea, real pretty, but in the end, the DSM worked against you Good luck with whatever idea you persue next, and for any more ?s, IM me!

 

[dsm_pup]

OWGTI & DOHCDave..................

very impressive!!