Fitting Maserati 3200 GT turbos to a Ghibli

Last year I decided to replace the turbos on my Ghibli with those from a Maserati 3200 GT. There were a couple of reasons why I wanted to do this: I wish to slowly upgrade and tune the car, which undoubtedly means increasing the flowrate through the engine; I wanted to reduce the lag time of the turbos; I wanted some more reliable turbos.

The early Ghibli IIs (like mine) came without blow off valves (see earlier post) and as a result, there's a good chance that the turbos on these cars will fail sooner than those fitted on the later cars, due to the constant spooling and stalling that results from not having blow off valves. However, my Ghibli had only done low mileage (around 55,000 km at that time) so the turbos were still in good shape. So it was really a bit premature to change them out... but the opportunity arose.

The turbos on the 3200 GT are technically more advanced than the ones fitted on the Ghiblis, since they incorporate a roller bearing package over the plain bearing package on the Ghibli turbos. The turbos for both cars were manufactured by IHI of Japan. The power side of the turbo on the Ghibli and the 3200 GT is the same except for the bearing package, denoted by the suffix letter in the product description, RHB for the Ghibli and RHF for the 3200 GT. The compressor side is larger on the 3200 GT turbos, which is not suprsing given that it's a 3.2l engine versus the Ghibli's 2.0l. However, I'm eventually planning on further increasing the maximum RPM, polishing up the heads and fitting a free-er flowing exhaust, so the additional capacity that the 3200 GT turbos cater for will eventually be utilised in my Ghibli.

The cost of the increased capacity of the 3200 GT turbos is increased lag time. However, this is offset by the bearing package on these turbos versus the Ghibli turbos; the lower friction co-efficient of the 3200 GT turbos means less resistance to rotation, which means that like for like they should speed up quicker than the Ghibli units. So, factoring in the fact that the compressor is larger on the 3200 GT turbos and therefore doing more work, the net effect is that the 3200 GT turbos spool up at about the same rate as the Ghibli turbos.

I was fortunate to acquire some nearly new 3200 GT turbos from David Askew Maserati Parts Service, with only 14,000 miles on the clock. I had them shipped directly to the Maserati specialist Auto Forza, where Jorrit promptly fitted the units for me, taking about 2 days since there was a bit more messing around than he had anticipated. The exhaust manifold on the 3200 GT and the Ghibli is obviously different, so the old manifold from the Ghibli had to be retained and re-used. This meant that they had to be carefully removed from the engine block and the old turbos, which is easier said than done given that the bolts seize up pretty tight here given the heat they're subjected to.

The new turbos were a very snug fit and the engine had to be lifted slightly at the front of the car to accommodate them. This was done by inserting some washers underneath the engine supports between the engine and body, lifting it about about 10 mm. Some material also had to be shaved off one of the new turbo housings (the right one I think) to prevent it from touching the body, particularly when turning.

Once fitted, it was a bit tricky to determine what effect the new turbos had had on performance. When I initially took the car for a dyno, it was giving around 310 hp but only producing 0.7 bar boost pressure. No one could figure out why the boost pressure was low, although 0.7 bar just happened to be the fail safe pressure for the OEM boost controller. There was no engine warning light and the chip tuners confirmed that the fuel map was being followed. We could only think that the car was running in safe mode, but no one, including Jorrit, could figure out why? It didn't seem to be the solenoid, particularly since this had been recently changed out after a similar previous incident when the car was found to be running again at 0.7 bar due to the solenoid not working.

Since we couldn't find a mechanical problem and the chip tuners at Rica Engineering swore that it wasn't a problem with their software, I decided to purchase a new boost controller, an e-Boost 2 from Turbosmart in Australia. I fitted the boost controller and completely removed the OEM solenoid (seems there's no feedback loop from the solenoid to the engine ECU since the car runs fine with the solenoid not connected). I took the car back to Rica and set up the e-Boost on the dyno. However, despite the car now producing about 1.2 bar of inlet pressure, the power output was down at about 270 hp!

It took a lot of thinking and running of a few tests (including a cyclinder leak test, which showed that the engine was in pretty good condition, with only 5% leak from most of the cyclinders, but oddly with 20% leak from the cylinder on the rear right). I was convinced that it was the exhaust that was the problem, so asked Jorrit to try swapping out the mid section with a known good unit (which he fortunately had in his workshop). He took the car for a drive and instantly noticed a difference! So it was definitely exhaust related.

When putting back the old exhaust, he happened to notice that one of the pins on the lambda sensor was bent and not connecting properly. He straightened the pin and connected it back. When driving the car with old exhaust re-installed, it was driving much better than previously, although I suspect that not as good as with the replacement exhaust. So the problem appeared to be with the lambda sensor, which means that the engine had probably been running in open loop mode, unable to correctly measure and interpret the exhaust gasses. This means that the car had probably been running rich, which would explain the drop in power. It also means that the catalysts have become junked, since running a rich mixture through a catalyst will end up seizing it up. I find it a bit odd though that the engine warning light did not come on when this was occurring? So I'm tempted to install a data acquisition system so that I can monitor the mixture myself and not rely on the ECU's electronics doing the right thing.

This would explain the results from the next visit to the dyno at Rica. Although the results were better, now putting out 328 hp, it was not as good as I had anticipated. I'd figured that the car should deliver about 360 hp given that I had been getting 327 hp before the turbo upgrade (since the car had been chip tuned previously and was now red-lining at 7200 rpm). I also set up the e-Boost again while on the dyno and noticed that the turbos were by no means hitting their limits; I was not able to get the sensitivity of the controller to overshoot the dialed in maximum boost pressure of just over 1.2 bar. This means that there's probably insufficient exhaust gas flowing through the turbos (i.e. that the turbos are too large for the current application).

I find this a little bit hard to swallow. Given the evidence, I'm convinced that there's a restriction across the catalysts that's robbing some power from the engine. Also, the restriction may cause sufficient pressure drop in the exhaust to restrict the gas flow from the engine, which would result in the turbos not spooling up so quickly.

Of course, there's only one way to tell and that's to try fitting a new exhaust and take the car on the dyno... I'm planning on doing this later in the year...

Korst Banden

I paid a visit to Korst Banden last week. I wanted them to have a look at the Ghibli so that they could measure up the wheels and give me some confidence about ordering the correct size wheels. To be honest, I was a little disappointed with the service there.

They didn't seem too interested in measuring up the wheels and I felt like I was telling them what to do rather than them offering me advice. I've a feeling that they're not really into customising wheels, rather offering direct replacement wheels and tyres. One of the younger guys in the workshop did come and have a look and seemed pretty confident about what I was proposing, but the older guy who was at the front desk seemed more interested in ordering the wheels and seeing if they fitted... which is fine if they're prepared to take the wheels back if they don't fit.

They did at least seem OK about trying out some different tyres once the wheels were fitted. He seemed a bit concerned about the tire selection for the front wheels; he thought there might be too much rubber on a 225/40 R18 tyre and thought that a 225/35 R18 tire may be more suitable.

I'm going to order the wheels with the same offset as the current wheels and they see how they fit; hopefully it will all work out and if the fit is too tight I may have to go with 215/35 R18 on the front and 245/30 R18 on the back, or get the lip rolled up. I'm a bit reluctant to go with the latter, since it will be a bit expensive gettting this done, since it will likely involve a paint job.

Guess I'll just have to wait and see...

PC wheels out of the running

After further emails with Korst Banden, the local retailer of Compomotive wheels in the Netherlands, it looks like the 3 piece PC wheels are out of the running since they're about twice the price of the MO wheels.

I sort of set myself a limit for how much I'm prepared to spend on wheels for the Ghibli and that's about 10% of the value of the car. Unfortunately, the PC wheels are just too expensive given the value of the car, although I do still think they are nicer looking wheels.

After some more emailing with Compomotive in the UK, I've received some better pictures of the wheels that I'll probably be ordering, with a center hub blank for an offset between ET30 and ET40.

This first one is of the proposed front wheel, 18" x 8" with standard silver finish. I'd prefer the spokes not to come flush to the face of the rim, but it doesn't look too bad. I'm also not too keen on having the Compomotive logo stamped on one of the spokes, but again I can live with it, bearing in mind the whole reason I'm after new wheels is not for cosmetic reasons, but to give me some more ground clearance without adversely effecting the handling characteristics of the car.

This second picture shows the 18" x 9" wheel that would be fitted to the rear of the car, this time with optional sparkle silver finish. I like the way the spokes sit further back in this wheel, giving it a bit more or a sporty appearance. The wheel shown has four studs, which I find a bit odd for this size of wheel?

Overall, I think they'll look OK on the Ghibli and after doing some more sums, I'm confident that they'll solve my ground clearance problems. I anticipate well over 20mm additional clearance at the front of the car, which should prevent the anti-roll bar infront of the engine sump from fouling with steep speed bumps.

Just behind the front wheels where the catalysts are located in the center of the car, there should still be about 20mm additional ground clearance with the new wheels. Maybe this doesn't sound like much, but I'm pretty confident that this will prevent about 90% of the fouling I currently get when going over speed bumps. If this turns out to be the case then I might even replace the catalysts with some new ones (since I'm an environmentalist at heart).

Further developments on the wheel front

I spoke with Jorrit yesterday and got some further insights into the Maserati Ghibli!

It seems that on the MY92 cars, Maserati left the lip on the inside edge of the wheel arches unfinished, so these stick out into the wheel arch at a 90 degree angle to the body panel and impair on clearance of the wheel. On the MY94 cars, presumably as a result of factory fitting larger wheels, this lip was rolled out on the top half of the wheel arch, increasing clearance between the body panel and the wheel.

As a result, on my MY92 Ghibli, I'm a bit more restricted on the offset that I can fit before I start getting interference between the wheel and the body panel. This means that the minimum offset on the MY92 cars is restricted by about 10-15mm from the MY94 cars, unless the lip is rolled up. Since this modification will necessitate a trip to the body shop (to get the metal resprayed after rolling it up) then I have decided limit the reduction in offset.

I also discovered that on the MY92 cars, the offset of the factory wheels (the seven spoke OZ Racing wheels) is ET35 on the front and ET32 on the back and not ET35 all around as I originally thought.

I enquired with Compomotive the prices of the MO and PC wheels, but they referred me to a local retailer, so I'm planning on making a visit to get the wheels properly measure up to ascertain the optimum offset specifications. They did however send me a nice picture of some 18" MO wheels fitted to a Ferrari.


These are 9" wide on the front and 10" wide on the back. I find them a bit delicate, which suits the Ferari, but not sure it fits the more agressive styling of the Ghibli. So I'll probably go with the PC wheels still.

For info, the Dutch retailer for the Compomotive wheels is Korst Banden BV.

Development on the wheel front

I've been doing some more thinking on the wheels. In addition to the space out described below, I've been thinking some more on wheel diamter and tyre selection and come up with the following schematic.


I've also been having a rethink on wheel selection, still from Compomotive in the UK, but a three piece modular wheel design, as pictured. I like this wheel because the spokes are set in from the front of the wheel, giving it a more sporty, agressive look. I also think they fit the style of the Ghibli, with a nice simple five spoke design. I'd prefer not to have the studded rim (and a bit worried that it will leak), but this does have its advantages with respect to maintenance if the rims get curb damage.

I think I'll go with an offset of ET30. I could probably get away with less on the rear, but I'd like to have the same wheels on the front and back so that I can swap them round if the fronts get some minor damage.

The increased overall wheel diameter at the front should give quite some additional road clearance; about 20mm on the radius to lift the car to about the same as an MY94 model. The tyre selection will still give me about the same amount of rubber around the wheel as I have currently, so resistance to curb damage to the rim should be the same as I have now.

On the rear, the increase in diameter will give an increase in the wheel circumference and hence a bit of additional gearing. However, this is less than 10% and I know that the speedo on my Ghibli currently overestimates speed by about 10% (I measured it late last year when driving back from Germany; the speedo was reading about 265 km/h but my TomTom was reading about 250 km/h). So it's still legal.

For tyres, I see that Bridgestone offers the sizes that I'm after in their Potenza S-03 range (Bridgestone Tyre Size Line-Up), i.e. 225/40R18 on the front and 255/35R18 on the rear (and suitable for speeds over 300 km/h!).

I'm just running the numbers past Jorrit at Auto Forza to check if the clearances will be OK. If he thinks it's all OK then I'll be placing my order soon!

Ghibli survives another winter

I took the Ghibli out on the road this weekend, after it's been wrapped up over the winter months. I reconnected the battery (after disconnecting it over winter) and it started up no problems straight away!

I drove it nice and carefully with low revs until the engine was warmed up. The only thing I noticed was that a lot of steam was coming out of the exhausts (when I stopped off at the local Shell petrol station to squirt in some Pura and a spot of injector cleaning fluid). This seems pretty typical of the car, particularly on cold, damp days.

I drove the car to Rotterdam and had a nice breakfast with the missus at Proef! On the way back I opened the car up a bit, mainly just to intimidate an Italian plated Lancia driver who was being very aggressive to the cars in front, flashing his lights and indicating that he wanted to overtake, so I thought I'd embarrass him a bit by leaving him standing. Anyway, the car performed great and I had to feather the throttle a little to prevent the rear tyres slipping on the damp road surface.

The Ghibli is now rapped up in it's new home; I purchased a garage space just down the road from our new house and now have the car parked next to it's new friend, an Audi A3.