All biturbo: body front weaknesses

alpa

Member
Messages
185
Hi,
I'd like to tell what I know about the fundamental design problems of the front part of all biturbo cars, from carbs up to qp4.
To briefly remind history (I don't pretend to know all the details): the biturbo body remained basically the same from carbs to qp4. First cars had the 4 bolts suspension and a 150hp engine, then came the 5 bolts with a much more performant steering on the same engine frame and engines of more than 250hp, then ghibli with wider track width and 300hp, then the tubular rear suspension and then the ZF diff frame.
But the body floors and frames remained the same in all these cars: same metal sheets made of the same chewing-gum black steel. Same weld points. Same design mistakes.
Worse, during the body assembly the ghibli front frames (made of the same carb mould) were cut to give more space to the engine.
Qp4 had a slightly redesigned body with some reenforced points and was likely made of a modern automotive steel. It's a guess about the steel people do because qp4 bodies are much harder to cut. Again, all design mistakes remained present.

So Ghibli had a more performant suspension, twice more power, better brakes, bigger wheels and weighed 150kg more than carb versions, but were still using the same body.
The body has huge design flows in the body frames that hold the engine frame. The structure is weak and is made of 0.9mm and few 1.2mm sheets. Not to mention 2 and even 3 layers of sheets above the engine frame that often rust in between and break.
The consequence is that when these cars are driven hard the front of the body breaks in many places. People continue driving these cars in this condition. A friend runs a Maserati workshop and he often repairs craked ghibli and qp4 bodies.
I've been studying these problems for years on my cars. The last time I had a "chance" to buy a '97 GT that likely made track days on slicks. The front is completely destroyed, although the car looks great. The body was repaired at least once but broke again few cm farther. The car was painted and everything was hidden under a thick layer of putty and painting.
So my car is a kind of study of the design mistakes because it broke in tens of points. Here are pictures. I'm not going to explain every picture, but I can add comments later, if needed.
Some pictures show past repairs with ugly and not that ugly welds.

One pictures shows the floor that was smashed in an attempt to straighten it. The engine frame was pushed inside the car because the structure is so weak.
 

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alpa

Member
Messages
185
More pictures
 

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alpa

Member
Messages
185
Here are pictures on an opened right side frame (longeron). All the body sheets are 0.9mm thick, except the one I marked as 1.2mm. On the picture with 1.2mm I've already started repairing and modifying, so many new welds are visible.
 

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alpa

Member
Messages
185
This picture shows the weak area that bends in the first place in case of a shock into a wheel. It's the right hand side, engine bay. The cross is the firewall, on RHD cars the cross would be replaced with the steering column hole. All sheets are 0.9mm thick and as you can see the connection is not orthogonal, there is a stock bend. In case of a shock the bend is bent even more, there is no mechanical resistance.
 

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alpa

Member
Messages
185
These are pictures of my '89 222E that made a 4m long flight. As you can see the body structure is the same as on the ghibli. The body frame was bent, the junction bent even more. A pictures shows what's inside the body frame: void.
The other picture shows the 1.2mm body panel I cut to open the frame. It's really bent looking from the inside, it's because they filled it with tin to make it look flat from outside. My flight was not the first accident of this car.
 

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alpa

Member
Messages
185
Btw, in the bottom part of this picture, just where the black putty starts on the frame there is a rectangle mark. It's a hole in the metal sheet that was used on biturbo cars to hold the torsion bar. Then starting from ghibli the bar was mounted behind the engine. But the hole remained because the body was still made of the same parts.

index.php
 
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Messages
397
Looks like a huge job, and only really practical with the engine out.

Despite your very thorough repairs, will this area not always be compromised and possibly break again in places?

What was it that led you to performing these repairs, was it something obvious such as handling or cabin noise, shuddering, etc.?
 
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alpa

Member
Messages
185
I did that because the engine was out (dead 1400km after a rebuild by a french "specialist", so I'm building a new engine. I bought the because of the engine problems so I drove it on 50 meters). But I knew about these problems, I did my red car 2 years ago, and I have a collection of photos of multiple ghibli/qp4 taken by a maserati workshop. I wanted to reinforce anyway, I knew these weaknesses, and I noticed traces of repairs in the wheel passages.

It's not a huge job, it's very local. 2-3 weeks, working 3-4 hours per day, are enough.
The problem is the alignment. In my case it was ok. Then you need to check alignment after evey modification, otherwise the weak structure distords.
 
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alpa

Member
Messages
185
I've already mentioned this in the other thread.
These pictures show how approximative was the body assembly on my '97 GT (never seen such a poor quality on older biturbo cars). The small bar on the right of this picture (that is usually smashed because idiots try to lift cars here) was not welded to the floor on about a half of its length. Same on the other side of the car. The next picture shows a closer view.
All welds are where I replaced the rusted floor.
This part of the body structure is supposed to be important, it links the engine frame to the rockers (rockers are the most rigid parts of the body and they form a kind of frame of the car).

20240327_171241_compress48.jpg

The gap was about 5mm large. It's all rusted below, despite the factory putty.

20240327_171245_compress7.jpg

Same on the other side of the car, the gap was 2-3mm large.
The rust below the lift support is common, the floor is not strong enough and it breaks. The absence of welds didn't help to improve the rigidity.

20240327_171329_compress11.jpg
 

alpa

Member
Messages
185
Despite your very thorough repairs, will this area not always be compromised and possibly break again in places?
It will and it did break again on my car: lots of cracks around old welds.
As I said the entire structure must be reinforced, including the firewall and the floor. There are sheets of metal to be added, all the empty structures have to be opened, some sheets of metal must be replaced with thicker plates (at least 1.2mm, better 1.5mm, in place of the factory 0.9mm).

Here are pictures of a non abs 2.8 ghibli owned by a very calm and careful man. Same areas as on the pictures of my GT

IMG-20240119-WA0024.jpg

IMG-20240119-WA0023.jpg

IMG-20240119-WA0021.jpg
 
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Messages
397
Just curious. Has your car ever been in a collision, even very low speed? Maybe not in your ownership but possibly before?
 

alpa

Member
Messages
185
Just curious. Has your car ever been in a collision, even very low speed? Maybe not in your ownership but possibly before?
No idea. The car came from Italy and was owned by at least 2 persons. Then bought buy a French, then by me (1400km later).

However I know a very skilled maserati workshop. The guy repaired tens of biturbo of all ages (from carbs to qp4) and has never seen cracks ahead the engine frame.