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plumdeplakmuis

Esprit GT3 (4cyl) primary shaft upgrade

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As we are rebuilding and upgrading the GT3 920 engine for improved power and torque I'm considering to modify the gearbox with a upgrade primary shaft. Either the Holoway kit or the GTOracing kit. My only concern is the new gearing on the 1st and 2nd gear. I frequently use the car for long trips around Europe which always contain some heavy traffic driving conditions. Is there experience with either a GT3 or other 4 cylinder cars with these kits? Especially with regards to the new gearing.  

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Hi Jaap,

Unless you are going way up the power scale , the upgrade kit is not needed..  you will only start to run into g/box issues  when using a later 027 box aggressively with over 350 ft lbs of torque, this will be upper 300's for bhp.  You will run into  other issues like the clutch way before then ..    As far as the gearing is concerned with the taller C/R GTO set up , 1st is very tall when used with the 3.89:1 CWP and 18 inch rear wheels. This produces 7.51 mph / 1000 rpm in 1st  as apposed to 5.95 on std 1st..... The GT3 box has the old 4.11;1 CWP  which will lower to 7.11 mph / 1000 rpm. against 5.63 mph / 1000 rpm std.  . Again with the 18'' rears..  if you have the 17'' wheel the figure will be lower still , this make its more acceptable  ..   The only other issue you need to consider is that the standard 4.11:1 CWP will not take the torque much over the 260 ft lbs mark so is a none starter straight away for tuned engines.   There were a batch of high torque 4.11:1 CWP made for commercial and racing use , but these are very few on the ground and very expensive...  It took GTO racing over a year to locate me one and that had too come from the states.. 

So to recap .        The upgraded kit is not ideal for use with the 4 cylinder Esprit's in stop start traffic . With a tuned engine you will need a 3.89 CWP  or a racing HT 4.11 CWP. preferably in a UN1 027 box.   A standard 027 box  with 3.89 CWP in good order used with consideration should handle 350 ft lbs with drive-ability..   At 409 ft lbs torque my standard as new 027 lasted less that 800 miles..     This info is based on personal data gathered while tuning the 4 cylinder Esprit.. 

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I’ve not managed to break the shaft yet.

2nd gear..... yes on the s4

CWP - smashed to bits on the v8.

theres time.....

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Thanks for feedback, definitely need to look into the CWP issue. 

We will be aiming ~350 hp, with the following updates:

  • Alunox / vdlee twin scroll, ball bearing turbo setup
  • EFI e4 ecu
  • Upgraded conrods
  • Deatchwerks injectors
  • Direct ignition coils on spark plugs
  •  PNM upgraded clutch

So with the new turbo setup we should improve low end torque supported by the upgraded PNM upgraded clutch. Although 350ft lbs sounds a bit high, I don't think we would go over 275ft lbs.   Car is now on the standard 17" wheels but considering 18" for the rear in the future.  

Then on the CWP i was not aware there were different specs, I can only find A082F6484F in the parts list but not sure which one this is. 

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If I’m not wrong - CWP was the same in all Renault boxed esprits. Dave @CHANGESwill know better

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I’ve got a spare one that’s smashed to bits 😂

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Hi Jaap, before you spend hundreds of ££££ on hardened diff gears you should consider the Quaife LSD, may cost a bit more initially but the benefits in reliability and getting the torque onto the tarmac will be money well spent.

Supplied by GTO engineering around £800.

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11 hours ago, plumdeplakmuis said:

We will be aiming ~350 hp, with the following updates:

  • Alunox / vdlee twin scroll, ball bearing turbo setup
  • EFI e4 ecu
  • Upgraded conrods
  • Deatchwerks injectors
  • Direct ignition coils on spark plugs
  •  PNM upgraded clutch

How much boost are you going to be running to get 350BHP?

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9 hours ago, Steve V8 said:

Hi Jaap, before you spend hundreds of ££££ on hardened diff gears you should consider the Quaife LSD, may cost a bit more initially but the benefits in reliability and getting the torque onto the tarmac will be money well spent.

Supplied by GTO engineering around £800.

Although I agree the Quaife  ''' ATB ''  not LSD  ( they have the same results but very different in design)   is a great asset and I notice a substantial improvement on performance conversion , it will not help protect the CWP.   In truth it will increase the loading on the CWP and make it more susceptible to failure...  This is down to its ability to minimise wheel spin which is a sort of release for the torque generated.   With a standard diff you will spin a wheel at a lot lower torque so reducing the loading on the CWP.           

The failure on second gear is mainly due to the synchro  popping.  this happens due to the ratio gap between 1 and 2 being a bit large .. As a result people rush the change , not letting the revs drop sufficient and overload the synchro, which eventually pops.    This is the situation where smooth is best not fast !   As for diff failures ,  Those that mostly fail on the 350 ft lb mark are due to snap changing.. This is when you spin the wheel or wheels in 1st then slap it into 2nd and back on full power. The torque load then release then load causes a spike in the figures that can strip the CWP.   It is not unusual to see the same people blow 2nd synchro  and the CWP..  (sorry Barry)  Its what we see on a lot of competition UN1 failures...   Good news is the GTO set up gets rid of the 2nd gear issue due to the close ratio set removing the problem cause.   The CWP will always be the week link , so race version and Cryogenic treated CWP will help. 

However if you are limiting yourself to 350 bhp,  which is probably wise unless you have very deep pockets , a standard UN1 027 type box with or without ATB will suffice your needs..  Just stay smooth on 1st to 2nd and it should give you good service..  

The other UN1 failure is the 5th gear shearing off...  This is a result of using 350 ft lbs + on and off whilst in 5th or aggressive power 4th on to 5th as in my case...  The overhung 5th flex's the shaft when these actions occur, causing fracturing by the oil undercut on the shaft and eventual failure..  This failure is a more prominent in the big BHP engine Esprit's. but rectified by the GTO conversion.. 

hope this helps

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Hello Jon, 

Not sure on the boost required yet. I suppose between 1 and 2 bar.

Thanks Dave, 

From SJsportcar I got the info that the GT3 pn for the CWP is A082F6584S while the S4s/V8 is A082F6484F so I will buy the V8 CWP. Still not sure on the GTO primary shaft, the changed gearing for 1 and 2 is not to my liking. I'm also checking the EMCO upgrade only EMCO's response is not great. 

 

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Hi Jaap,

You may want to look at the g/box as a whole not just the CWP.    The GT3 box is the UN1 028 and it is not only the diff ratio that is different, some gear ratios are also different.   It has long been known that the 028 is not compatible with even the standard 2.2 or 910 turbo.  It may be the gear specs on a whole are all lower as the max torque on the GT3 std set up is only 217 ft lbs.. .. 

Also matched sets of CWP  are very rare now, mismatched not so.. but be aware...  A recon 026 or 027 would be a cheaper and easier solution to your needs. 

 

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Thanks Dave,

I ordered the V8 CWP from SJSportscar. Now changing to another gearbox is a bit to late. Maybe in the future first I will try my luck with this setup.

Cheers,  Jaap

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When my v8 blew up - Lotus had availability of CWP sets

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My gearbox went recently, and it turned out to be the diff. I had the short throw gear mod done, so I’m wondering if that contributed to it. My car puts out about 290 ft lb of torque. I’ve put the gear change back to normal now. I never do boy racer wheel spin starts though, so I assume it just hadn’t been setup right when it was last rebuilt about 5,000 or so miles ago.

The CWP was fine apparently, but I bought a new one anyway, and did indeed have it cryogenic treated. I didn’t see it before it went in, but Chris Cole who rebuilt my box did comment that it definitely seemed different to a standard one!

And yes, the CW and Pinion are still readily available. I can only assume it’s a common Renault part across a number of different boxes.

Edited by Glyn Harper
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12 hours ago, Glyn Harper said:

And yes, the CW and Pinion are still readily available. I can only assume it’s a common Renault part across a number of different boxes.

Renault CWP's and Lotus CWP's  are of different quality and strength.  Renault versions will not take the torque of the Lotus ones..   Just be aware, !!!  One may fit all but is not always correct..     Also very as few people really drive their Esprit's aggressively,  even when the wrong part is fitted it may not be an issue for them...     This is becoming a problem with all second hand Esprit's and Un1 boxs , in the way that you do not really know what you have till it goes south....  So buyer beware... The Renault versions will be cheaper , but there is a reason.. Also just because its expensive does not mean you are not buying a pup..  Do your homework check the component source, don't take the suppliers word for it,   After all its you that has to pick up the pieces ... 

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If the backlash isn’t set up correctly the diff and CWP takes a proper lashing - 5000miles and failure is massively common it seems when this is the case. I know of six gearbox failures all at roughly that mileage 

13 hours ago, Glyn Harper said:

My gearbox went recently, and it turned out to be the diff. I had the short throw gear mod done, so I’m wondering if that contributed to it. My car puts out about 290 ft lb of torque. I’ve put the gear change back to normal now. I never do boy racer wheel spin starts though, so I assume it just hadn’t been setup right when it was last rebuilt about 5,000 or so miles ago.

The CWP was fine apparently, but I bought a new one anyway, and did indeed have it cryogenic treated. I didn’t see it before it went in, but Chris Cole who rebuilt my box did comment that it definitely seemed different to a standard one!

 

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Sorry, yes.. you're both correct in that I did get a proper Lotus CWP from SJ Sportscars, but those also do seem to be readily available still.

And yes, the chap who previously rebuilt my gearbox about 5,000 miles ago was a generic gearbox guy (no disrespect to him) and not a specialist on these type of boxes, so I gather it was setup badly due to lack of understanding of the Lotus setup.

Chris Cole did my rebuild so I'm hoping it'll be a bit better now. He did ask me if it had been apart before (he could tell) and then went on to tell me it was now setup correctly!

Last job to do today is to fit new Rivnuts to hold the under tray on, and I'm back on the road! Still a few little jobs I want to do (change the clutch and brake fluid) but they're not holding me up taking it out for a bit of a test drive.

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