turbo n00b with some pretty silly questions
06-11-05, 11:46 AM
#1
blenderhead
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turbo n00b with some pretty silly questions
hi all,
i have a 89 TII, bone stock except for a corksport power series exhaust and a set or stainless brake-lines i'm gonna put on this weekend.
so... i've never owned a turbocharged car before so maybe i dont completely know what to expect, but i'm pretty sure this is abnormal operation. let's start with what i see on the boost gage. i'm idling, the gage is at zero. as i speed up through say 2-3k RPM it raises to around 1/4 of the way up the scale. this is fairly consistent. its what happens after beyond that that varies from day to day. if i punch it at this point, what usually happens is, the car accellerates, the boost needle drops to zero and a deep whine that i assosciate with the wastegate increases in volume. this happens right away, not when i'm up at 7k. its almost always a smooth linear acceleration too, with nothing that feels like a lagging turbo kicking in. of course, sometimes, especially if i dont push the pedal all the way to the floor, i get the shot of boost at about 3500 or so. sometimes i get the turbo whine, sometimes it sounds like the wastgate opening.
leading theories from friends and colleges include.
also, there's oil on the airhose coming from the intercooler. im hoping this doesnt mean i have a bad turbo that needs a rebuild.
that's the main problem i'm having. there are others of course, but this is the one that has the most immediate effect. another is this weird phenomenon i only experience in 5th gear when i get up to 80mph where i give gas, the RPMs increase from 3-5k and the car maintains the same speed. oh, and the wastegate opens up. weird huh?
thx in advance for ur help. i'm trying to be reasonably DIY here. i'd hate to actually have it tuned by a professional or something
i have a 89 TII, bone stock except for a corksport power series exhaust and a set or stainless brake-lines i'm gonna put on this weekend.
so... i've never owned a turbocharged car before so maybe i dont completely know what to expect, but i'm pretty sure this is abnormal operation. let's start with what i see on the boost gage. i'm idling, the gage is at zero. as i speed up through say 2-3k RPM it raises to around 1/4 of the way up the scale. this is fairly consistent. its what happens after beyond that that varies from day to day. if i punch it at this point, what usually happens is, the car accellerates, the boost needle drops to zero and a deep whine that i assosciate with the wastegate increases in volume. this happens right away, not when i'm up at 7k. its almost always a smooth linear acceleration too, with nothing that feels like a lagging turbo kicking in. of course, sometimes, especially if i dont push the pedal all the way to the floor, i get the shot of boost at about 3500 or so. sometimes i get the turbo whine, sometimes it sounds like the wastgate opening.
leading theories from friends and colleges include.
- worn out wastgate spring
- faulty boost gage
also, there's oil on the airhose coming from the intercooler. im hoping this doesnt mean i have a bad turbo that needs a rebuild.
that's the main problem i'm having. there are others of course, but this is the one that has the most immediate effect. another is this weird phenomenon i only experience in 5th gear when i get up to 80mph where i give gas, the RPMs increase from 3-5k and the car maintains the same speed. oh, and the wastegate opens up. weird huh?
thx in advance for ur help. i'm trying to be reasonably DIY here. i'd hate to actually have it tuned by a professional or something
06-11-05, 01:29 PM
#2
Your boost gauge should read vacuum (less than zero) at idle. I suspect the gauge has a faulty connection. Is this the stock gauge or aftermarket?
Without trustworthy gauge readings (or experience to know what boost feels like), who knows what is happening. All cars make more noise when you get on the gas, so don't expect to be able to identify a unique "wastegate opening" sound. Maybe your wastegate actuator rod is disconnected from the wastegate flapper door, preventing your car from building any boost. Get the boost gauge sorted out first, though, so you can accurately assess what's going on.
I am fairly certain that the 3-5K rev but no speed change thing is a worn out clutch. It will get worse if you have a boost problem and fix it (thus increasing the power your car makes). You need a new clutch.
-Max
Without trustworthy gauge readings (or experience to know what boost feels like), who knows what is happening. All cars make more noise when you get on the gas, so don't expect to be able to identify a unique "wastegate opening" sound. Maybe your wastegate actuator rod is disconnected from the wastegate flapper door, preventing your car from building any boost. Get the boost gauge sorted out first, though, so you can accurately assess what's going on.
I am fairly certain that the 3-5K rev but no speed change thing is a worn out clutch. It will get worse if you have a boost problem and fix it (thus increasing the power your car makes). You need a new clutch.
-Max
06-11-05, 02:34 PM
#3
blenderhead
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thx max, i figured it was the clutch, but i though it was strange that it only happened in 5th. i can actually hear it make noise when i depress the clutch pedal.
i just have the stock boost gage in the original gage cluster. i guess tonight i'll break out the manual and see if i can find the vacuum hose. it only reads less than zero when the engine is off...
i just have the stock boost gage in the original gage cluster. i guess tonight i'll break out the manual and see if i can find the vacuum hose. it only reads less than zero when the engine is off...
06-11-05, 02:47 PM
#5
5th gear puts the greatest load on the clutch (the balance between "car moving" and "clutch slipping" is tipped the most toward "clutch slipping" in 5th gear, versus the other gears), so that's when it slips.
Some change in the noise is normal when pressing/letting go of the clutch pedal. With your foot off the pedal, the transmission is turning (and making noise), with your foot on the pedal, the tranny stops turning. Other parts can make noise, too, but in general there is no tell-tale noise when the clutch is worn out. It just starts to slip.
Are you sure you are reading the gauge correcly? Boost/vac gauges are quite strange in that they have 0 in the middle, a pressure scale (kg/cm^2 a.k.a. "kilograms per square centimeter", or something like that) above 0, and a vacuum scale (like mmHg a.k.a. "millimeters of mercury") below zero. Lets start by identifying the units of measure on your gauge so we can make sense of the readings you get. What are the pressure units? If it has a vacuum scale (some gauges only read pressure), what are the vacuum scale units? For instance my aftermarket gauge reads in "psi" for pressure, and in "inHg" for vacuum.
-Max
Some change in the noise is normal when pressing/letting go of the clutch pedal. With your foot off the pedal, the transmission is turning (and making noise), with your foot on the pedal, the tranny stops turning. Other parts can make noise, too, but in general there is no tell-tale noise when the clutch is worn out. It just starts to slip.
Are you sure you are reading the gauge correcly? Boost/vac gauges are quite strange in that they have 0 in the middle, a pressure scale (kg/cm^2 a.k.a. "kilograms per square centimeter", or something like that) above 0, and a vacuum scale (like mmHg a.k.a. "millimeters of mercury") below zero. Lets start by identifying the units of measure on your gauge so we can make sense of the readings you get. What are the pressure units? If it has a vacuum scale (some gauges only read pressure), what are the vacuum scale units? For instance my aftermarket gauge reads in "psi" for pressure, and in "inHg" for vacuum.
-Max
06-12-05, 12:20 AM
#6
blenderhead
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well, i'm not nearly confident enough to claim that i'm reading it correctly, but i've been studying it for several weeks. it's the stock boost gage in an FC instrument cluster. it looks kinda like this
http://corksport.com/store/image/a5b...89/91Turbo.jpg
except that it's orange on black. the gauge goes from -30 to 0 and then is gradated from 0 to +45 mmHg. during normal driving between 2-4k RPM, the needle sits about 1/4 of the way up from 0-45. when i accelerate beyond that, it drops to 0.
it's raining like a mother up here. maybe tomorrow i can actually open the hood =)
http://corksport.com/store/image/a5b...89/91Turbo.jpg
except that it's orange on black. the gauge goes from -30 to 0 and then is gradated from 0 to +45 mmHg. during normal driving between 2-4k RPM, the needle sits about 1/4 of the way up from 0-45. when i accelerate beyond that, it drops to 0.
it's raining like a mother up here. maybe tomorrow i can actually open the hood =)
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