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1986 740T - Turbo+ kit, Hwy noise, Trans conversion[740-760/1986] posted by Lorno on
Saturday, 25 April 1998, at 8:32 p.m.
I own a 1986 740 Turbo wagon (160,000 km) that I have some questions about.
1. The car is fitted with a factory turbo+ accessory.
-What is it exactly and how does the turbo+ kit work?
-How can I determine if the turbo+ kit is working properly, short of taking
it to a shop?
2. The car is uncomfortably loud on the highway when the throttle is applied.
The noise (low pitch howl from the engine) is only apparent when the gas
peddle is applied (even a little bit), otherwise the car is quiet.
- What might this noise be and is it normal?
- Are there any noise suppression accessories available?
i.e. hood blankets, firewall insulation etc..
3. The car is fitted with an automatic transmission.
- How realistic a job is it to convert to a manual trans?
- What items (aside from the obvious) would be required?
Thanks
Lorno
Re: 1986 740T - Turbo+ kit, Hwy noise, Trans conversion[740-760/1986] posted by Steve Seekins on
Tuesday, 28 April 1998, at 7:59 a.m.
The turbo + kit basically changes the boost curve allowing higher boost, but only at higher rpm. Under full load and with your foot to the floor, you should see the boost needle climb close to the end of the yellow boost range.
There are lots of things that may prevent this. Problems with pre-detonation (ping) will be sensed by the knock sensor and retard the timing. Hot weather and poor gas will cause this. Broken or loose exhaust bracket at the bell housing will sound like knock with same result as will many other mechanical noises. Some can be caused by failed motor mounts allowing metal to metal contact by tranny cooler lines, oil pan to cross member, etc.
Another common problem is a misadjusted throtle plate. Even after correctly adjusting all the linkages, if the throttl plate does not fully open so that it is EXACTLY parallel to the bore at full throttle, you will not be able to get anywhere near fulll power from the engine.
If this is the case, you will need to remove the throttle linkage from the throttle plate lever and slightly bend the lever away from the throtle body (toward the front of the engine). This will effectively shorten the length of the lever so that the same amount of linkage travel will cause more rotation of the throtle plate. Reattach the link and check the full range of motion again - repeat until the throttle plate goes from idle stop to exactly full open. While you are at it, clean the throttle body - any dirt also affects full throttle performance.
Find those buzzing noises. look for loose parts, broken brackets, collapsed or failed motor mounts, pipes or lines touching or too close to frame or other parts. Remember that under load, the engine moves - it will torque over some on the mounts and some parts that do not appear to touch may do so as the engine moves.
Look for problem in intake plumbing. Is the air filter installed? Check for proper operation of the radiator fan and its thermostatic clutch. Check transmission.
Steve Seekins,
Thursday, 30 April 1998, at 2:38 p.m.
Turbo+ is similar to saab APC unit...it bleeds the signal to the turbo wastegate, allowing a higher boost than normal. It only allows this at full throttle (there's a terminal on the throttle position sensor or idle switch that is installed and used to tell the turbo+ the throttle is wide open).
Test for turbo plus operation by plumbing in psi boost gauge to manifold...don't use the line that goes to the turbo wastegate signal because that one is being vandalized by the turbo+!
On a clear road in second gear get full boost WITHOUT full throttle; use the brake to keep car speed down and get max boost around 4000 rpm...don't hold on the brakes for longer than 10 seconds...record max boost level.
After a brake cooldown period, redo the test with your gas foot to the floor...you should get considerably higher boost....around 14 psi.
No increase in boost means the turbo+ isn't working.
There is a separate fuse for the turbo+...on my car the fuse is in a 1"X2" white plastic block cable tied to the driver's side wire harness near the driver's side strut tower.
Also, the turbo+ works by bleeding air to atmosphere from a solenoid valve mounted next to the turbo+ circuit board on the front of the airfilter box...if the bleed hose is pinched shut it won't bleed and turbo won't plus.
I prefer the 4 speed automatic to the standard when coupled with the turbo and city driving, others might not. Not worth converting to manual...if you're going to do that (convert to manual) you might as well convert to a chevy or ford v8 and the associated 5 or 6 speed manual.
Noise from the engine could also be a collapsed hydraulic motor mount(s). Check for the engine oil pan almost touching the crossmember...engine torque will cause the pan to touch the crossmember and all kinds of noise comes through.
Not unusual for hydraulic motor mounts to go almost every 120k....known weak spot and really irritating. Also, what kind of muffler/resonator is installed...the stock volvo cans are relatively quiet behind the stock cat...any changes such as eliminating the rear resonator or front muffler can make them noisier than stock.