audi tt losing bo0st??

  • Thread starter Thread starter jr0ck
  • 34 comments
  • 3,144 views
J

jr0ck

Messages
172
when racing my slightly modiffied audi tt (full drive train, weight redux., stage 2 turbo, t2's, full supension, etc....) ive noticed i lose bo0st presure when acceleraating. i to0k into account a recent discussion of the benifits/drawbacks of using a lightened flywheel on a turbo'd car at one of my hangouts (dsmtalk.com) and tried to apply my new found knowledge. i realized with the mild hp i was running (308hp i think) maybe the racing flywheel wasnt the best choice. from what ive come to understand, lightened flywheels reduce the rotating mass on the drivetrain, therefore reducing the load on the engine. well a turbocharger produces bo0st from the exhaust gasses of the engine under load, and when this load is reduced, although the engine will rev more freely and quickly, the load is less so peak bo0st it reached at higher rpm, therefore reducing the time the car is producing max hp. well i changed back to a stock flywheel to increase the load on the engine and maybe sustain bo0st for the length of my powerband to no avail. so to put a long story short, my modded auid tt loses bo0st while racing and i don't know why. any help would be aprreciated...:)
 
my r32 gtr vspec ll maintains 2.0 bar bo0st as long as im mashing the throttle. so not all of them do it :D

and NO, turbo lag is the feeling of "waiting" for the trubo to spo0l and produce the horsepower of the desired bo0st setting. the waiting comes from a lack of exhasut fumes that is required to spin the compressors blades, very common with huge "snail shells"...ie.BIG FAT TURBOS with bigger blades to spin:D :D

and i forgot to add, the reason why losing bo0st while acclerating is strange because it shouldn't happen. the harder the engine works, the higher the rpms sho0t up, the more exhaust produced, the faster the turbo's comnpressor wheel spins, the more bo0st created....it could go on for awhile but u get the point :D
 
Originally posted by jr0ck
my r32 gtr vspec ll maintains 2.0 bar bo0st as long as im mashing the throttle. so not all of them do it :D
Click to expand...
"They all" as in all Audi TTs. ;) I highly doubt you'd be able to tune it out, and same goes for the SLK and a small handful of other cars.
 
That's the Audi TT's characteristic in the game. If you want to know why, then I guess the answer's in the Audi TT fan club forums or some of the people here own Audi TTs, or neon_duke will come in here and start talking about the lost in boost. Let's see what happens :)
 
well thats re-assuring to a point, but now it's going to b a tune-a-thon to try and to set the audi tt straight!!! but now the question is....why do only audi tt's do this?? does it occur in the s4 also??? the world my never know....
 
I searched on Google.com and I found out that the intercooler also plays a role in the boost pressure. Here's what it says:

Intercoolers (IC's) usually do not give large power increases but rather allows you to run higher boost levels without problems such as detonation or pinging/knocking. However, by cooling the intake charge with a larger IC HP gains of approx. 1% per 10 degrees, minus whatever boost losses you get. If the IC flows the same as stock and drops the charge temp 50 degrees on a chipped motor you would get about 10hp. BUT usually a larger IC does not flow the same as stock and you will lose some boost due to the larger volume, as well as longer intake pipes (depending on style of intercooler). An intercooler upgrade is not needed for cars that have just a chip.

Source: http://www.18turbo.com/18t-intercoolers.html
 
to each his own Sominon...sc's are ok for low to mid speed cars but eventually the engine catches up and u have no more drive for ur belt...turbo's for top end and most agree on effeciency since its run on exhaust fumes. turbo's, depending on bo0st, can be there only "when u need them" but sc's are always "on". oh well this isnt sc's vs. tc's :D :D :D


and thanks for the ic info Thio, ill see if that helps in tuning...
 
It depends on the situation. If you want to have a burst of energy at the top end, then turbo is the way to go. If you want to have better performance just slapping on a compressor, then supercharged is the way to go. I might as well spend the money that I would spend on a supercharger just tuning the engine itself instead of installing something that would rob power away from the engine.
 
I just read a recent issue of Hot Rod, and they compared a turbocharged, to a centrifugal blower, and a roots style supercharger. They hooked each one up to a 5.0 Ford engine, either bored or stroked to a 327. The turbo had the best torque curve and horsepower curve. And in the end, the turbo had the biggest torque number, with a slightly lower HP rating than the centrifugal blower.
 
Excellent QUESTIONS & ANSWERS Guys !!!
:D Good to see another GREAT Thread.
I'm going off topic a little to ask if anyone remembers the Lancia Rallye car ( the REALLY UGLY one way before the one we have in Gt3) that had BOTH a Roots Supercharger & a Turbo??? The supercharger had a clutch similar to one found on an air conditioning compressor hooked to a sensor & a "Flapper" valve. The "Blower" would work @ Low RPM until sufficient boost was developed to make the Turbo work right. Then the "Blower" would dis-engage & the Turbo would take over. If RPM fell too much the clutch would re-engege, the flapper would open & the "Blower" would take over until sufficient pressure was re-establihed by the turbo. Think they actually got it to work pretty well...UB57
:D
 
Originally posted by Sominon
Wouldn't that still be uneeded clutches and pulleys et cetera to weigh down the engine?
Click to expand...

:D The weight of a clutch (5 lbs maybe) is negligable & more than offset by the tremendous torque advantages a "Blower" offers @ relatively Low RPM. While a Turbo is idling along doing nothing a "Blower" is churning out GOBS of Torque filled HP. Rallye cars need HP Throughout the RPM Range & 15+ years ago there was no "Computer Management" to make Turbos "Work" like they do today. It was a pretty wild feat of engineering in it's day...UB57
:D
 
well Quattro, i cant comprehend how the 1.8 can produce enough exhaust to reach full bo0st at say 4k rpm but lo0se bo0st pressure proportionatley (sp?) up to its 6k something redline:confused: :confused: :confused: (unless this is the worst case of bo0st creep i've ever seen)...

i worked a 12 hr day yesterday so i didnt have time to tune like i would have liked and i still have the bo0st "leak". even though im going to try a few more combo's of parts, im kinda getting that feeling that sage was correct in the fact that tuning wouldnt iron out this "problem":irked: :banghead:

im glad u like the thread UB57, im glad its gotten go0d responses as well:D :D , and ive heard of tWo other "twin charged" cars in my automotive "research"(to fun to be considered learning:lol: ).
the meguirs' ITR that was super street awhile ago(when i was a borederline ricer :O :D :lol: ) and an old mr2 that was in SCC's ultimite street car challenge awbile back as well. the meguirs' ran fine, with the help of comp. managment, but couldnt bo0st very high. the mr2 barely ran but it came across like a garage chop job so it was pretty impressive for the average joe to have accomplished. well back to work, enjoy.........
 
the undisputed king of turbo lag in gt3 is the...............Escudo, i mean it kiks in at like 6,000 rpms
 
um .... Thanks for talking about something else ... :werd:

jr0ck, have you tested the Audi TT with your new bound skills yet?
 
the answer is pretty simple here guys...when an engine is at a higher rate of RPM, the engine requires a higher volume of air. the turbocharger is making its "boost" between the piston top and the intake manifold. if the engine is sucking in more of this air...the turbocharger is no longer as effecient as it was and the boost level is lower. this trait of losing boost with rpm is quite common on most factory turbocharged cars...this drop in boost can be fixed by doing a number of things. (boost controller to actuate the wastegate, different intake manifold, larger turbocharger, mounting the turbo a different distance from the cylinder head.) this is why some cars utilize a primary and secondary turbocharger(one mounted closer to the cylinder head to spool quicker and provide low rpm boost, while the other is mounted further away from the cylinder head so that it takes longer to spool, thereby covering the higher rpm where the primary turbo would begin to loose boost.) the Audi TT and Evo both have a single turbo charger on a low displacement engine...try it out on a twin turbo car and see if the boost reduction is lesser ;)
 
Maybe the head just doesn't flow enough to move that much air? Even with port and polish, there is still a limit to now much air will flow through it. *shrug*
 
Originally posted by e1eveN
Maybe the head just doesn't flow enough to move that much air? Even with port and polish, there is still a limit to now much air will flow through it. *shrug*
Click to expand...

what i said wasn't a guess lol, try what i said..and you'll see that GT3 is realistic in its turbo physics.
 
I know, and I agree with you. You would think that a turbo upgrade that costs 75 grand wouldn't have problems maintaining boost. :D

However, small displacement engines are quite capable of maintaining high boost pressure. A stock Evo runs over 2 bar with no problems. They might not be as efficient in the upper revs, but they don't lose boost. The physics involved in small displacement single turbo engines aren't that different from larger displacement twin turbo engines. It's just scaled down a bit. They might not have as much exhaust with which to generate boost, but they have less air to move.

I think that made sense :confused: Feel free to smack me when I start rambling.:p
 

Latest Posts

Back