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Low powered V8 0.35 - 0.4 maximum boost - frequency valve issue ?


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Guest modifiedv8engines

Hi All

 

Here we go again

 

Finally got around to getting the Esprit through the MOT test and taxed, insured and ready to go. at faster than I should be doing motorway speeds car is unstable. Close inspection of road springs and another over large road hump through town has resulted ina broken front road spring.

 

Not that I should be going too quickly with the car having these handling traits ( springs on their way for fixing weekend) but............

 

Appear to be getting only 0.35 -0.4 boost irrespective of whether engine is cold or warm and or gear selected.

 

Installed and set new forge motorsport wategate acuators as per the good book  so that 0.35 mechanical boost has been set which equates to 0.4mm of rod movement. Used mityvac gauge and took some time to get right

 

Initial thought was that more movement required in the rod to up the boost  however

 

Book says boost frequency is responsible for adding additional boost to 0.75 bar providing there is no det or other system malfunction

 

Suspect the boost frequency valve is at fault ........anyone had similar issues ?? or worse ECU £££???

 

Perfromance is at present a bit dull and to get some real forward motion "blur" foot has to be flat on the boards to acheive golf GTi type performance

 

 

 

Thanks in advance ..........

Paul

 

 

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Have a look for the bleed valve - it's about 5cm x 3cm, on the right side at the very back of the engine bay attached to the firewall.  It will have a two wire electrical connection and a hose connected to the top and another connected to the bottom.

 

First of all check the electrical connector is secure (but I'd be very surprised if that was the issue since if it's disconnected you immediately get a CEL). 

 

Next check the top hose (from the throttle body) is secure. Try connecting your mityvac gauge to this hose and rev the engine hard to see what sort of psi you're getting.  Alternatively you could check the hose routing back to the throttle body for any lose connections. It goes through the right side of the engine bay under the quarterlight panel toward the front of the engine, back into the engine bay and connects to the throttle body.

 

Finally (and be VERY careful doing this), you could try disconnecting the bottom hose.  This means the wastegate actuators won't receive any positive pressure and therefore shouldn't open, regardless of the manifold pressure.  So there nothing to prevent the engine overboosting, up to the limit of the T25s (which is about 2.1 bar).  This allows you to check the wastegates and turbos are able to produce more that the 5psi boost that you're seeing.  It'll be blindingly obviously if the engine is boosting freely.  First of all without the ECM feeding the boost in gently, you'll get a near instantaneous VERY sharp throttle response (don't try it on a corner!)  Secondly it will only take a relatively small throttle opening (about third to a half) to reach 11psi. It's a somewhat blunt approach but will straight away rule out any problems downstream of the bleed value.  Just be very gentle and only ever feather the throttle.

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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Guest modifiedv8engines

Thanks for that Neil,

 

Checked out the frequency valve today and connections to this and the other hoses that connect up next to the ECU - these all appear to fine and good and tight. Also checked the hoses to  the wastegate actuators and again doesnt look to be a problem in this area either. Pulled the cover from the off side quarter panel and both hoses ( one that enters the rear wing from the rear near header tank and the other from frequency valve) and all looks to be okay

 

Spoke to Phil @ SWLC who reckons it could be the boost/frequency valve as these are only a simple magnetic switch solenoid which can get lazy if left standing about. The valve looks fairly crummy so is probably the original one from new so could be this. 

 

May pull this if I get time friday and see if adding some voltage results in movement of the switch......may need vacuum as well and it may just be easier to replace this if the last test proves the turbos and wastegates are workign okay

 

I like the last choice - had 1 bar boost some time ago before i pulled the engine and transmission for various repairs - happened on a slight bend and was lucky or skillful ( I like to think skillful) to avoid ending up on the wrong side of the road.

 

If its all working as it should this will make up for the last few hundered miles of less than entertaining motoring. Note what you say about the boost coming in quickly .......like a light switch so need to watch for this.

 

Thanks again Neil

 

Paul

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Guest modifiedv8engines

Thats a pint I owe you Neil !!

 

Removed red hoses from the boost solenoid valve and road tested. Third gear and once warmed up the engine pulled like a train. Proves as you said that everything is working correctly other than the boost valve.

 

Get one of these ordered Monday ...........£90 + VAT and carrige seems a bit steep and no doubt this is from Lotus only. If anyone has a parts cross ref for this that would be good

 

Thanks again

 

Paul 

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I would get Peter's free OBDII scanner and see what WGDC is being commanded by the ECU. There could be a problem in the ECU also.

The Older I get the Faster I was

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Yeah, it is somewhat addictive running an overboosting V8!  Really shows what it could have done had it not been for the limiting factor of the gearbox.

 

The V8's MAP sensor only reads to 2 bar so you can't see what the max boost the T25s could produce.  But I ran an OBDII trace and you could see from the slowing rate at which the boost was increasing that it would top out at approx. 2.2 bar. But the most surprising thing is just how instantaneous the boost comes on without the ECM to feed it in gently.  Again this was primarily to protect the gearbox.  But I'd imagine another factor was to prevent a lot of V8s ending up in the bushes due to an over ambitious use of the throttle in the bends!

 

Overboosting my V8 was how I managed 179mph at VMax back in 2005:

 

http://www.vmax200.com/vmax-X.php

 

The timing beams were 1.6 miles down Bruntingthorpe's 2 mile runway, using the rest to slow down. The car was still pulling well through the timing beams, it would have been interested to see what speed it could have managed over a longer distance.  On that occasion, overboosting the engine was actually a calculated exercise.  You'll see from the photos that it was very cold, below freezing for the whole day.  I worked out the night before that the inlet air temp running 2.2 bar with that ambient temperature would be roughly the same as 1.75 bar on a hot summer day.  So there was method in my madness!

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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Guest modifiedv8engines

New frequency /boost valve fitted and now seeing an improved but flickering 0.5 BAR boost approx. on the gauge. In 5th gear @ apprx 75 MPH, WOT sees 120 MPH in a fairly short space of time and there is the feeling of potentialy much much more perfomance to come.

 

Previous to this and the gauge showing 0.35 BAR the Esprit would have struggled to see probably 130 - 140 MPH tops 

 

Power seems good so expect the boost gauge is a bit tired.  

 

Gather the later cars had no boost gauge so anyone know the procedure for checking ?

 

Appriciate any assistance etc  

 

Paul


Indeed Neal

 

The overboost condition is addictive and my car which I think is running pretty much as it should doesent have that get up and go like it did when the boost pipes were disconected ........i liked that a lot  

 

Lotus worried about cars ending up facing the wrong way or similar .......nah never. Didnt bother Porsche much either when they unveiled the 911 Turbo

 

When I worked at Lotus there used to be several factory visits by potential customers. Part of the sales thing was to take potential customers around the test track in the then 215 BHP Turbo Esprit.

 

With a good driver, and a clear track those cars were very quick in both acceleration and deceleration - many of the customers thought the cars could be driven like this on the road. Many soon returned to the factory smashed, bashed requireing new chassis and lots of bodywork.  

 

Testiment to the GRP and general design of the chassis, many walked away un-scathed which was suprising given the amount of damage to the cars. My brother (poor sod) used to do the chassis (headache) changes back in the day when the serice garage was at the factory

 

Couple of my drinking buddies used to work in the test cells in engineering and lets just say due to "problems" the engines and gearboxes were restricted to a 350 BHP limit. The V configuartion of the Lotus engine was not best for vibration apprently but if he engine had been designed as per the usual American V8 configuration then the engine woulnt have fitted ........apparently

 

Anyway that aside     

 

Anyone got a spare set of chips or an ECU from PUK or similar that they are not wanting any more ??

 

Let me know ...cash waiting

 

Paul

Edited by modifiedv8engines
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One thing to be aware of if that with the standard ECM, you only get the full 11psi boost across the rev range in fifth gear.  In the other gears the boost becomes progressively greater as you go up the gears, but is still only 6-8psi up to around 6k rpm.  Only above 6k does it increase further, reaching 11psi as you hit the redline:

 

bgraph.pdf

 

(ignore the overboost curve, as far I know that only applies to the Lotus Red Race ECM)

 

I'm starting to sound like a broken record but again this was done to protect the drivetrain, since the car's acceleration or more precisely the torque at the wheels, is higher relative to the increasing overall gearing step-down.

 

You mentioned getting a set of Marcus's chips.  But to be honest, unless you're after more that 11psi (and are prepared to take the additional risk), the best update you can get is to have Lotus reflash your ECM with the Sport 350 code. It 'only' costs a few hundred quid (when I had it done a fair while ago, I've no idea of the price now) and has the major advantage that Lotus can reflash it without touching the ECM in your car.  No soldering or anything else which might damage your precious and very, very, expensive ECM.  In fact I don't think Lotus stock the V8 ECM anymore and you can't even get one from a scrap dealer since they'll only sell it with the engine.

 

With the S350 code, the boost curve for gears 2, 3 and 4 becomes the same as fifth gear.  First is still restricted but traction is typically the limiting factor anyway so that's no real loss.

 

I can't emphasise enough the how much of an improvement the S350 code is.  It behaves like a completely different car and you can really power through the gears without dropping off boost.

 

Regarding your boost gauge, I don't suppose you have an OBDII scanner?  That allows you to read the inlet manifold pressure directly from the MAP sensor.

Edited by neal

May: DON'T hit it with a hammer!

Clarkson: Why?

May: Cause it's the tool of a pikey.

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Guest modifiedv8engines

Thanks for taking the time in getting back to me Neal

 

Appears the reflash is no longer available from Lotus or main dealer network They didnt seem to know what I was talking about which to be fair is probebly due to the many years since last production of these cars.

 

According to a couple of independant Lotus dealers, the firmware or means to do this was sold off to another company but no-one seems to know who this is/are ?? 

 

Seems as though I am stuck with the standard ECU programme and any power enhancements will need to be undertaken by improving efficiency i.e, intercoolers and possibly tweaking the turbo wastegates a little.

 

Hear what you and others have said about uprating the transmission and since this was rebuilt less than 500 miles ago I am not really that keen to drag it out again and then sport out the high cost of the one piece output shaft from GTO.

 

My car already has KN filters, 200 CEL cats (probably worth about 10 BHP if that ) etc and seems to go okay but doubt it would see the claimed 170 odd MPH. Think that your car was an exceptional one or if not carefuly set up as Top Gear had real problems getting close to what you acheived.  

 

Do you have a list of what you did to acheive the high top speed Neal ?

 

Think the Mike S car was a quick vehicle but despite looking cant seem to find what spec that motor was or how the transmission held together with what must of been well over 450 realistic BHP .

 

Would like to see some real data on engine power outputs (corrected) for standard and up rated engines if anyones got them available ... Lotus or anyone else ?

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At Donington Brian Angus did a talk on the various Lotus engines and he recounted a story of testing the V8 at a circuit (I think in Italy) around a hillside and achieving 189mph.

Dave - 2000 Sport 350
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Forgive me if wrong but I had understood that the V8 unit was the 32 bit ECU from EFI in Italy? MT501 IIRC.

 

The code was developed by Ole Buhl Racing who I believe are now UK based not Denmark.

Surely even without the software and hardward to flash the EEPROMs in MT501 you could just physically install the aftermarket chips?

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Guest modifiedv8engines

Update

 

Had a call this afternoon from Lotus Service ( thanks Chris) and although the reflash may be available apparently...... its not.

 

The guy I spoke with said that this was due to the possibility of transmission damage and although it could be done there would need to be signed disclaimers.  

 

There was also mention of the driveshafts being not so much weak but with more boost = more power the possibility of damage or failure in this area also.

 

And Dave - think Brian Angus must of meant Nardo in Italy which has a banked circuit.

 

Even the Lotus Excel SE ( driven by my late father) and a couple of early Esprit's NA and 215 BHP Turbo where all reaching 145 + MPH on that circuit. At that time the slightly more powerful Excel ( Excels gave another 8 - 10 BHP due to the longer exhaust and tuned intake ram pipe) was faster than the NA Esprit. Lotus added the rear wheel arch spats to slow the car to preserve the diferentials which were prone to failure.

 

So no doubt a good Esprit V8 with everything as it should be and running correctly could attain a very high top speed.  From Neals description of his car @ Bruntingthorpe, his speed was recorded short of the 189 MPH but as Neal said, a greater top speed with more road could have followed.

 

Cheers Pete

 

Been warned off the chip replacement route as physical damage can occur if not carried out correctly. Reflash would be the easiest and relatively strightforward or even tunable to allow say 10 psi instead of 11 for example. Given the ECU's are no longer available I wouldnt want to take the risk ( as sensibly advised by Neal)

Edited by modifiedv8engines
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Think the Mike S car was a quick vehicle but despite looking cant seem to find what spec that motor was or how the transmission held together with what must of been well over 450 realistic BHP .

 

 

Hi Pete,

upgraded BE bearings

forged pistons

flowed/ported cylinder head

twin chargecooled

hybrid gt2860 compressor turbos

custom ECU

GTO upgrade 5-speed with 3.44/1 cwp

 

Peak boost: 1.1 bar

Power: 507bhp

Torque: 437 lb/ft

Inlet temp: peaking 40deg C

 

http://www.thelotusforums.com/forums/topic/28742-esprit-v8-project/page-16

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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Hi Mike!

Hope everything is well with you.

 

Paul,

My comment about ECUs was more that Lotus should be able to flash one of these with the standard code rather than some enhanced performance version.

I'll have to check but I'm sure I read somewhere that the Exige S1 ECU has the same part number as the V8 one?

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Guest modifiedv8engines

Thanks Mike, Pete, Neal and everyone else for the informations

 

Sorry for droning on about this but

 

Took my car out again this evening and although its been a warm day ther is a nice cool breeze this evening so reasonably good for a road test.

 

Engine seems to be seeing approx 0.5 Bar boost in 3,4,5 but when doing say 80 mph "on the track" ....flooring the throttle doesnt really make for rapid progress. And I mean my foot is to the boards and Im waiting for the engine to pick up . Pass 6000 rpm in 3rd and still not seeing any more boost ........120 in 5th and the same story

 

Getting full throttle and have already checked that. No MIL light or anything untoward on the temp gauge ( sitting at an indicated 80 - 85 deg C)

 

Dont know if my expectations are too high but although the car feels reasonably quick, its not kind of "electifying" as you would expect with around 290 ish RWHP and 1250 Kg or thereabouts.

 

On the route home on a busy B road, 3rd gear and foot to the boards and the car takes off, front of car seems to rise and you get the feeling that only lots of power can give .......nice push in the back and everyhring starting to live in fast forward mode 

 

On return home, I let the engine idle for a few minutes before shut off and there appears to be a faint exhaust popping now and again which sounds a bit like a misfire but its not. This is similar to ingress of rain water around the spark plugs and if you have ever experienced this its very similar.

 

Plugs were changed when engine was out 500 mies ago and leads were changed for those magnecore leads. 

 

Im thinking possibly an air leak or even the road speed sensor is causing an intermittent boost/power fault.

 

Assuming Im getting an intermittent air leak ? then would/could this cause the variable power and not so much power scenario due to one of the sensors possibly MAP sensor seeing "lean"and reducing ignition advance and correspondingly... boost pressure to compensate ? 

 

Any tech guys who know how the system works or who have had similar issue please enlighten me

 

Cheers

  

 

 

 

  

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I tried to analyse what it felt like the engine was doing in this thread:

http://www.thelotusforums.com/forums/topic/54595-intercooling-v-ecu/

 

So yes, it does seem similar. Summer afternoons and evenings the car feels quite 'tame' by comparison and looking at the calculated IATs would support the idea that the ECU is backing off the waste gate duty cycle and 0,5 bar is in the ballpark.

 

The only time when it feels like all the performance is available are those nice cold mornings in autumn and winter. Once ambient is below 5°C it is a different animal.

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Guest modifiedv8engines

Thanks Pete

 

Bit stuffed as cant read any engine data via the ODB link for some reason but suspect there is a similar issue with my car to yours. However with my car its a bit of a lottery as to whether you get full boost (0.5 BAR) or less or 0.6 BAR as I acheived on one occassion yesteday

 

I am sure I have an air leak somewhere ( intake manifold, plenum area possibly) as after my attempts to get some data on the laptop yesterday, and following some WOT testing, engine rpm takes longer to decay to idle speed,than is normal.

 

With low speed gear shifting, engine rpm rises during changes so it feels like the throttles are partialy open and  not closing.

 

 

  

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As far as gearchanges are concerned I have always had the same where the ECU will hold the revs up via the IAC valve. Probably to avoid the sudden drop of revs that may catch out unsuspecting drivers, ie unsettling the rear when letting the clutch out with mismatched revs/speed.

 

Have also noticed that the IAC seems slightly affected by high temperatures so maybe after a WOT test session it took longer to return to a stable idle setting?

 

Logic would assume the boost solenoid to be at fault (especially when I heard that some dealers regard them as 'consumables') but you've already changed it....maybe even sticking wastegate?

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Spoke to Mike S about the slow rpm decay sometime ago and removed the SAI and EGR to hopefuly erradicate this issue.  

 

Also in the last 500 miles replaced boost capsules, crank sensor, IAC valve, boost sensor as well as numerous other parts

 

Although I cant obtain the ODB data at this time, I am convinced of an air leak somewhere is causing a lot of the engine running issues. A weak mixture from say a leaking manifold joint or crack, bad sealing injector  or ? will cause the ECU to reduce igntion advance, dump more fuel and lead to the elevated rpm situation. 

 

Probably easier just to remove the intake plenum and carry out a visaul inspection but the OBD data would save some time and I would have someting written doen to analyse

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Guest modifiedv8engines

Anyone got any IAT data they can share

Managed to get some data from the ODB port but lap top configured to auto off after 15 minutes.So only a small amount of data to look at

Amazed at the high inlet temperatures 75 deg C even with only 25% engine load and coolant @ 83 deg. C

Note Mike S car with over 500 BHP seeing a very low 40 deg C peak !!!

Like to know if my data is normal ( manual says upto 130 Deg C....or should that be deg. F ) so clearly a intercooler is much needed for these cars not just for performace but for longevity !!

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Paul

 

There are two one way valves on the V8 one at the front of the engine bay and one at the back near the throttle linkage

 

If you remove them you should only be able to blow through them one way if intact

 

Mine were both shot allowing boost to be vented and excess air to be consumed

 

They are something to do with the breather system,oil mist over a period of time tends to make them stick open

 

Regards

 

Dave

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Thanks for that Dave

My air leak was found to be from the clear tube that runs from the EGR valve ( under the plenum) which I have now replaced.

Pipe had fractured causing excessive air and engine rpm set at an elevated 3500 - 4000....difficult to drive in traffic and stopping at the traffic lights was a bit embarrassing to say the least.

Now getting approx. 0.5 BAR boost ( new solenoid fitted) but still not seeing anymore on the gauge which may be inaccurate anyway.

Driving normaly and slowing for a junction for example, Im still getting a slow engine speed decay to idle until the car stops under braking and then, and only then, does engine speed settle to approx 1000rpm. Engine rpm can after extended idle period of say a minute, decay to a low 600 - 650rpm

Seems as though somethings still not quite right even though the engine pulls much better, and moreso in th evenign when its cooler

So symptoms are I feel air leak related and it may well be the case that its the non return crankcase breather valve you mention (possibly the one near the TB) . Get on to this later today

Thanks for the advise Dave.....something else to eliminate

Paul

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One way valve knackered (crankcase breather) so ordered this and item sent was indeed a one way valve but not the right one (typical) bit of messing about and fitted - still only getting less than 0.4 BAR boost.....gauge flickering

Managed to obtain some data using Peters software and although throttle cable and pedal adjusted as per the Lotus manual - not seeing full TPS 100 % or anywhere near

snapshot of values as follows :

Acceleration in 5th Gear from 60 - 95 MPH and boost gauge reading 0.4 BAR - WOT

And to recap

No MILS lights

New Forge wastegates set up correctly

New Radiator

Removed air con rad as it tend to block air flow to what appears an already marginal cooling system

EGR and SAI removed, ports plugged and not connected

Engine Load 31%

Outside Air Temp 23 deg C

Coolant Temp 66 deg C ( may be the cause for less than expected boost ?? )

WGDC 9%

Intake Temp 41 deg C

Road Speed data 94 KPH road speed according to speedo 94 MPH

Engine rpm 3699

Intake Pressure 121 kPascals

Baro 101.5 kPa

IGN Advance 16 deg.

TPS 37%

Pulse Width RH Bank 9156

Pulse Width LH Bank 8312

Lamdas all within range

So it would appear its only when +75 deg C coolant temp is reached ( but IAT rising) that more than 0.4 BAR boost is acheivable. With increased IAT then efficiency is reduced and subsequently power...seems a odd ball way of doing things - Just have to wait until winter to get the best power and then cope with cold tyres ......

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  • 4 weeks later...

Paul -with around 1/3 of TP used [eg. 37% way on the pedal] , why do you think you have to get more than those 'around 0.2bar' ?

 

 ..what you do there is a simple 'cruise'  type of testrun.  The speed you postd, those 94km/h is not much of a challenge for a V8 Esprit, as up to 38-45km/h you can do with simply 'high idle' in 5.-gear position ..without touching the loud pedal at all

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