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stebro exhaust

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hello,

i just installed a new stebro exhaust on a US 1997 lotus esprit (V8). i noticed that after installing the exhaust system, the boost on the turbo's top end at about .3 bars. with the stock exhaust, they would top out at .8 bars or so. i am going to remove the new exhaust and install the old one to confirm that it is the exhaust that is causing the drop in boost or it was there before and just did not notice it.

i guess my question is as follows: can a change in the exhaust (muffler) cause a change in the turbo boost? if yes, is there something that needs to be done on the turbo's?

thank you for reading this post

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Out of curiosity, how does it sound?

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I doubt it's the exhaust unless it's blocked.

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i just verified that my boost issues is not related to my exhaust, since i installed the old exhaust and i still have the boost issue. i saw a write up on using a hand pressure vacuum pump and a dial gauge to check the wastegate setup. has anyone done this? if yes, do you have to remove the wastegate or can this be done while it is installed on the car. also, is there a dial gauge setup that someone can point me to? thanks

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something like this ? :

"..ED.11 - TURBOCHARGERS AND EXHAUST MANIFOLDS

A Garrett T25 turbocharger is used for each cylinder bank, mounted on a short cast iron manifold at each

rear side of the engine bay. The turbochargers feature water cooled bearing housings and integral wastegates,

operated by a pressure capsule. The pressure line between the turbocharger compressor outlet and the

wastegate operating capsule is routed via a frequency valve, in order to permit boost control by the engine

management ECU. The turbochargers are not handed, and as such require different designs of exhaust manifold. Each cast iron manifold maintains separate gas streams for cylinders 1 & 4, and 2 & 3 (RH cylinder bank), and cylinders 5 & 8, and 6 & 7 (LH bank) up to the turbocharger turbine intake, in order to optimise pressure wave effects, Nine stainless steel studs and self locking nuts are used to secure each manifold to the cylinder head, with a 3-laminate steel gasket sealing the joint. Each turbocharger is provided with an oil feed for its fully floating turbine shaft bearings, from an oilway in the cylinder head via a tapping at the outboard centre of each head. Oil from the turbocharger returns to the sump via a drain pipe directly into the side of the sump. The turbocharger bearing housing is cooled by the engine coolant in order to help control oil temperature and prevent carbonising during heat soak conditions after engine switch off. The coolant supply is tapped off the front end of the cylinder block outboard water jacket, and is returned to the rear end of the inboard jacket. Steel braided hoses are used for coolant and oil

feed plumbing, with additional heat protective sleeving on the LH oil feed and LH coolant return hoses. The wastegate capsule and actuating rod are calibrated by the turbocharger manufacturer to limit the mechanically controlled boost pressure to 0.35 bar (5.0 Ib/in2), representing the base setting which can be increased by the ECU controlled frequency valve bleeding pressure from the capsule pressure line. The base setting can be checked using a using a dial gauge and hand operated pressure pump with 0 - 1 bar (15 lb/W) pressure gauge:

- Mount the dial gauge against the end of the actuating rod.

Connect the pressure pump directly to the capsule, and record the pressure required to produce an

actuator rod movement of 0.4 mm (0.015 in).

Specification = 0.34 - 0.36 bar (4.9 - 5.2 lb/k-G).

If necessary, adjust the actuator rod length after removing the

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yes, this is the write-up that i am referring to. i was wondering if someone has actually done this, and how the dial gauge was attached to the rod and if the wastegate assembly had to be removed from the car

thanks

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you can probably use an type of *multi-angle* magnetic holder on the exhaust/catalyst pipe, put the dial on it and it should work.. .

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wasn't that our all 'set as stock-'reference ?

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wasn`t *high tq* just that overboost in the lower gears. something to wide the torgue curve up in lower gears an rpm range !? So would say it`s the purple line you should use as reference..

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Yes, it would be very close to the purple line. Here are the boost curves for the High Tq code:

V8_ECU_Boost_350.jpg

To the OG poster, if boost is .3 bar across the rev range, I would look to make sure you are getting full wide open throttle then make sure the boost solenoid was working.

If the car can hold normal boost for a few secs the falls off to .3 bar, I'd look for tired wastegates, boost leaks or bad turbo.

Edited by gmendoza

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answer to gmendoza question:

when the rpm reaches about 4k-5k the boost goes to zero. my theory at this point is that i have an issue with the ECU or the solenoid that keeps the wastegates closed when throttle opens @ 95% until the boost reaches about .8.

i downloaded a pc OBD2 program from someone on this forum and i am waiting for my ELM interface to arrive. i will then see what the ECU tells me.

thank you all for all the posting, very helpful

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Replace the wastegate solenoid first...cheap part & you can do it yourself...The solenoid fails over time & once it fails you'll be getting minimal boost. Easy way to test is to disconnect the connector (not the hoses) from the solenoid & go out for a drive. if it feels the same then it's likely your solenoid is bad.

BTW...post some videos of your new Stebro exhaust.

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that is exactly what i was going to do first, replace the wastegate solenoid. thanks for posting. i will definetely post a pic of the new exhaust.

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i just replaced the wastegate solenoid and no improvement. i actually downloaded an ODBII application for the V8 esprit on this forum and found that there are no codes on the ECU, but the wastegate duty cycle remains at 0%. i checked and all hoses are connected, not sure what to try next. any thoughts?

thanks

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