88 Turbo Esprit Runability Issue

[Ferrari guy]

Some time ago I posted a runability issue with a customers Esprit turbo. Now We are Ferrari guys and have a limited expierence with turbocharged cars.

Our issue was on hard accell around 4000 rpm, the engine seemed to be rev limiting, like the old rev limiting rotors on early German cars. The power curve seemed to hunt, power up, and then shut down, power up and shut down.

Being Ferrari guys we know a thing or 2 about cam timing and timing belts, so we degreed the cams and installed a new factory belt. We replaced the cap, rotor, the pick up in the distributor, new plugs, wires, coil, and ignition module. None of the above made a bit of difference. Next we checked and rechecked everything in the fuel injection system, pressure, delivery, relays water in the fuel system, all checked out perfectly.

We had a few responses to our previous post here, we followed all input and it did not make a slightest bit of improvment. The interesting thing was all emissions were spot on, all voltages exact,

Our next thought was an issue with the turbo. Turbo was in perfect operating condition and free running. We checked the hard line between the turbo and the pop off valve, no carbon.

Then we checked the pop off valve and it seemed a bit sluggish in its operation. I ordered a kit, and a new valve and spring. We installed the above parts and still the same problem extisted. We even removed the exhaust system to make sure we did not have a plugged exhaust, no change.

We reposted and no new information offered. So I decided to just drive the car on the freeway and watch the gauges to see if there was something that we may have missed. If I throttled up easily beyond the afore mentioned 4000 rpm, pressing lightly on the throttle it accelerated fine. If I pushed the pedal hard it ran up to 4000 grand then it started to rev limit on and off, on and off.

Thats when I noticed when hammering the throttle the boost jumped up + 11 pounds and the rev limiting started. I installed a test boost gauge to double check the one in the car. The numbers and results were the same.

So my conclusion was for some reason the boost was exceeding the built in limiter and it was shutting the fuel supply off, not long enough to starve it but just enough to cause a hesitation under hard accell.

We went back to the turbo and rechecked everything, and finally found the problem. While the pop off valve was operating perfectly and worked as intended. What we did find was a worn valve stem hole in the cast iron pop off valve housing. It was worn oval and was causing the valve to stay shut under load allowing the turbo pressure to build up and shut down the fuel supply.

We removed the valve and machined the oval stem hole round, then we machined a phosphor bronze valve guide and pressed it in place. We then reemed to fit, with the heat generated in that area we allowed more clearance than we would with engine valve guides. Due to heat expansion of both the valve stem and pop off valve housing we allowed .007 clearance.

We reassembled the valve and fired the motor up. Took it our for a quick road test and problem solved. The car is now a rocket, fast hard throttle accelleration up to 7 grand. Our initial problem seemed to get worse with higher temps so we blasted up the freeway for 30 plus miles and then returned. This Lotus runs strong and smooth with very nice powerful acceleration, at running temps.

Its now a nice fun car to drive with steady accell and it does run strong. Sorry to be wordy but with these cars getting a bit long in the tooth I'm sure others may or are expierencing the same issue. Turns out to be a rather inexpensive and easy fix. Once you remove the pop odd valve any machine shop can install bronze guide and problem solved. By the time you throw in a new valve, a pop off repair kit and new spring, the whole project should come in under $500.00.

Ferrari guy

[lotusespritse]

Thanks for posting! I am forwarding to a friend with similar symptoms on his 86 Turbo.

[sleekgt]

Definitely thanks for the follow up - as an 88 Esprit owner, I'm always looking out for information like this to help with preventative care.

>Thats when I noticed when hammering the throttle the boost jumped up + 11 pounds and the rev limiting started.

Interesting - I have noticed a VERY intermittent boost reading of 0.7-0.8 (about 11 PSI) after a heavy throttle LIFT OFF. It is a very rare occurance, but I have seen at least twice. I attributed to a flaky boost sensor, but this posting cautions me to watch these events a little more closely.

[ESPREE]

Originally Posted by Ferrari guy

we allowed .007 clearance.

This is most appropriate for an Esprit.

[sleekgt]

Quote:
>Originally Posted by Ferrari guy
>we allowed .007 clearance.
>>
>>This is most appropriate for an Esprit.

I saw that - it was really funny as it was so subtle and without an emoticon

[BlackSheep]

Does the car have the K tronic, dual webbers, or ac delco efi? You could of gotten any of the three in 88.. My 88 (with k-tronic) can't keep up after 10psi and goes lean.. Not sure if there is a boost cut off on any of them, as I have never tried to push it that hard. May want to look for an overboosting problem and if you are hitting an overboost cut off.. 11psi seems high to me. Does it cut out if you are not in boost? or only in boost?

[sleekgt]

Originally Posted by BlackSheep

Does the car have the K tronic, dual webbers, or ac delco efi? You could of gotten any of the three in 88.. My 88 (with k-tronic) can't keep up after 10psi and goes lean.. Not sure if there is a boost cut off on any of them, as I have never tried to push it that hard. May want to look for an overboosting problem and if you are hitting an overboost cut off.. 11psi seems high to me. Does it cut out if you are not in boost? or only in boost?

My 88 is a US spec Bosch CIS system. There is a boost limiter (a fancy relay that cuts fuel flow as Ferrariguy mentions) and the waste gate (which I believe Ferrariguy calls a 'pop off valve') on the 88. Currently my boost gauge implies the waste gate spring is weak as it only hits 0.5 bar most of the time (it should be hitting 0.65). Sometimes it will hit 0.60 bar, but it is random.

In my case, the '11 psi' number is not clear if it's 'real' or gauge/sensor error. I don't notice any fuel flow cutoff or slow down. And since it occurs randomly on throttle LIFT OFF, it's very difficult to diagnose.

When revving to 6K, the car is flawlessly smooth and powerful. It recently passed California smog test just fine - no indication of anything wrong except the boost gauge reading. It may be a phantom error, but warrants watching the boost gauge closely.

[StevenD57]

So my question is now that the Lotus runs right, is it faster than the equivalent Ferrari of that year? :-)

[lotus4s]

Thanks for taking the time to give us the update Ferrari guy.

[shill68]

Originally Posted by sleekgt

Interesting - I have noticed a VERY intermittent boost reading of 0.7-0.8 (about 11 PSI) after a heavy throttle LIFT OFF. It is a very rare occurance, but I have seen at least twice. I attributed to a flaky boost sensor, but this posting cautions me to watch these events a little more closely.

Theoretically, that makes sense if you don't have a blow off valve between your turbo and throttle plates. When you let off the gas suddenly, the turbo has still pressurized the plenum since the throttle plates are after that and if I remember right, the plenum is where the boost reference is taken. It makes sense that the boost would still register for a second after the throttle plates are closed. That and the gauge is probably a bit lazy at this age.

[MRDANGERUS]

Eddie,

You wrote:
"My 88 is a US spec Bosch CIS system. There is a boost limiter (a fancy relay that cuts fuel flow as Ferrariguy mentions) and the waste gate (which I believe Ferrariguy calls a 'pop off valve') on the 88. Currently my boost gauge implies the waste gate spring is weak as it only hits 0.5 bar most of the time (it should be hitting 0.65). Sometimes it will hit 0.60 bar, but it is random."

INSPECT YOUR W/G to determine if you have an Aluminum spacer ring brtween the main upper housing and lower "dish" cap.
If you do, then your w-g is de-tuned, perhaps down to 7psi boost (8mm ring) or 5 psi (12mm ring).
By removing this ring, the w-gate boost could be restored to 9.5 psi. This adjustment is NOT recommended for pre-HCI engines, though.

[s2mikey]

Originally Posted by StevenD57

So my question is now that the Lotus runs right, is it faster than the equivalent Ferrari of that year? :-)

It should be very close. The 328 was stronger than the 308. My '87 HCi comfortably puls away from my friends '84 308 QV. I havent had a chance to test against a 328 but I suspect it'd be close. Off the line, the Ferrari may pull a little stronger but when the turbs kicks in... Id think it'd be very close. Top speed will go to the Ferrari. Oh, and the Ferrari wins on the sound too, even though the Esprit doesnt sound bad at all.

[delomike1049]

Originally Posted by s2mikey

It should be very close. The 328 was stronger than the 308. My '87 HCi comfortably puls away from my friends '84 308 QV. I havent had a chance to test against a 328 but I suspect it'd be close. Off the line, the Ferrari may pull a little stronger but when the turbs kicks in... Id think it'd be very close. Top speed will go to the Ferrari. Oh, and the Ferrari wins on the sound too, even though the Esprit doesnt sound bad at all.

Nothing beats 80s/early 90s Ferrari V8s for sound. Nothing.

[carbuff]

Originally Posted by Ferrari guy

Then we checked the pop off valve and it seemed a bit sluggish in its operation. I ordered a kit, and a new valve and spring.

FG,

Where did you get the new poppet valve?

I just disassembled my WG and found that the chrome coating is worn on one side of the stem.

[CALOTUS007]

Originally Posted by Ferrari guy

Some time ago I posted a runability issue with a customers Esprit turbo. Now We are Ferrari guys and have a limited expierence with turbocharged cars.

Our issue was on hard accell around 4000 rpm, the engine seemed to be rev limiting, like the old rev limiting rotors on early German cars. The power curve seemed to hunt, power up, and then shut down, power up and shut down.

Being Ferrari guys we know a thing or 2 about cam timing and timing belts, so we degreed the cams and installed a new factory belt. We replaced the cap, rotor, the pick up in the distributor, new plugs, wires, coil, and ignition module. None of the above made a bit of difference. Next we checked and rechecked everything in the fuel injection system, pressure, delivery, relays water in the fuel system, all checked out perfectly.

We had a few responses to our previous post here, we followed all input and it did not make a slightest bit of improvment. The interesting thing was all emissions were spot on, all voltages exact,

Our next thought was an issue with the turbo. Turbo was in perfect operating condition and free running. We checked the hard line between the turbo and the pop off valve, no carbon.

Then we checked the pop off valve and it seemed a bit sluggish in its operation. I ordered a kit, and a new valve and spring. We installed the above parts and still the same problem extisted. We even removed the exhaust system to make sure we did not have a plugged exhaust, no change.

We reposted and no new information offered. So I decided to just drive the car on the freeway and watch the gauges to see if there was something that we may have missed. If I throttled up easily beyond the afore mentioned 4000 rpm, pressing lightly on the throttle it accelerated fine. If I pushed the pedal hard it ran up to 4000 grand then it started to rev limit on and off, on and off.

Thats when I noticed when hammering the throttle the boost jumped up + 11 pounds and the rev limiting started. I installed a test boost gauge to double check the one in the car. The numbers and results were the same.

So my conclusion was for some reason the boost was exceeding the built in limiter and it was shutting the fuel supply off, not long enough to starve it but just enough to cause a hesitation under hard accell.

We went back to the turbo and rechecked everything, and finally found the problem. While the pop off valve was operating perfectly and worked as intended. What we did find was a worn valve stem hole in the cast iron pop off valve housing. It was worn oval and was causing the valve to stay shut under load allowing the turbo pressure to build up and shut down the fuel supply.

We removed the valve and machined the oval stem hole round, then we machined a phosphor bronze valve guide and pressed it in place. We then reemed to fit, with the heat generated in that area we allowed more clearance than we would with engine valve guides. Due to heat expansion of both the valve stem and pop off valve housing we allowed .007 clearance.

We reassembled the valve and fired the motor up. Took it our for a quick road test and problem solved. The car is now a rocket, fast hard throttle accelleration up to 7 grand. Our initial problem seemed to get worse with higher temps so we blasted up the freeway for 30 plus miles and then returned. This Lotus runs strong and smooth with very nice powerful acceleration, at running temps.

Its now a nice fun car to drive with steady accell and it does run strong. Sorry to be wordy but with these cars getting a bit long in the tooth I'm sure others may or are expierencing the same issue. Turns out to be a rather inexpensive and easy fix. Once you remove the pop odd valve any machine shop can install bronze guide and problem solved. By the time you throw in a new valve, a pop off repair kit and new spring, the whole project should come in under $500.00.

Ferrari guy