Ghibli GT -96 Max Power

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goranw

New Member
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23
I have modified and tuned a friends Ghibli GT 2,8L -96 as much as possible without mechanical modifications of the engine and without anything visible from outside and with all equipment working as normal (AC, instruments and more) and the car should have drivability as a “normal¨ car. The engine was completely overhauled ca 7000 km´s ago. Specification: Fuel pump changed to Walbro 450, Intercoolers changed to QP4, Tubes from Turbo to IC increased from 41mm to 51mm diameter, same as IC inlet and outlet. Same for tubes from IC to manifold. Exhaust front part changed to Tubi with two 100 cell metallic catalysts, one for each side, rear exhaust is custom made 2 1/2” with one small straight through silencer on each side. Turbos are from 3200 Assetto Corsa. Clutch is Sachs Racing. Engine management system is changed to a MaxxEcu Race. The harness from the new ECU to the car was made as a plug-in harness so it attaches to the Cars harness instead of the Weber Marelli ECU´s. We use the car´s standard sensors only added a 60 -2 trigger wheel to pick up the rpm from the crankshaft. The SEM wastegate valve was changed to a MAC valve. Injectors was changed to Bosch EV14 714cc. Ignition modules was changed to fit the new ECU. Weber fuel pressure regulator was changed to one from AEM set to 3,5bar. One Bosch Lambda sensor LSU 4.2 on each side and one K-type temperature sensor in each exhaust manifold. Ethanol sensor so it is now a flex fuel car. The car was mapped and tested on a Dynomite Hub dyno. The car owner wants the engine to behave as much as possible as a NA engine so we held back the turbo pressure at lower RPM and increased it more and more with RPM to get the characteristic he wants. Otherwise, we could have got much higher torque on lower RPM. The results: On 98 Octan standard fuel; 379,2HP @ 6050 RPM (339,3 wheel HP) 514NM @ 4500 RPM (460,3 Wheel NM) max Turbo boost 1,4 bar. With E85 423,6 HP @ 5950 RPM (379,4 Wheel) 553,2 NM @ 4400 RPM (495,5 wheel) max turbo boost 1,5 bar. This was the absolute maximum the engine delivered, higher boost or changed ignition did not give anything more it was totally stop at this power output. Maximum injector opening time at E85 was 83%. The exhaust temp about max allowed 950 deg, almost hitting 1000 deg. With two deg higher (earlier) ignition pinging occurred at top RPM. Higher turbo boost did not give any more power eighter. Our conclusion is, this is the end for the small IHI turbos, they are too small, the turbine is probably to narrow and cannot let more exhaust out.

96139
 
A

alpa

Member
Messages
185
Very interesting !

Why to change all the intake pipes if you don't change the Y which is ahead the throttle body ? It's the bottleneck.
714cc is a bit huge for 70hp. Was it easy to set up the idle ? What's the pulse width in idle ?

3200gt make 370hp stock and there is always a margin in the turbo sizing.
My hypothesis is that the engine is limited by too narrow intake ports and small valves, see here:

I wish I could afford a Dynomite Hub dyno
 
G

goranw

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23
alpa said:
Very interesting !

Why to change all the intake pipes if you don't change the Y which is ahead the throttle body ? It's the bottleneck.
714cc is a bit huge for 70hp. Was it easy to set up the idle ? What's the pulse width in idle ?

3200gt make 370hp stock and there is always a margin in the turbo sizing.
My hypothesis is that the engine is limited by too narrow intake ports and small valves, see here:

I wish I could afford a Dynomite Hub dyno
Click to expand...

I Change all pipes to the same diameter as the IC´s. The Y was sanded to 42 mm same as the throttle diameter. Y is not the bottleneck its the throttle. As the injectors was 83% opened it was the right size. Idle is absolutely no problem with EV14 and a modern engine management system.
 
A

alpa

Member
Messages
185
On 2.0 GT the throttle is 2 x 44mm, you could use it.
However I don't think this would help. I'm sorry.
First if throttle is 2 x 42 and the Y is 2 x 42 then they are equally bottlenecks.
Second I was talking about the Y as the bottleneck of the pipes you modified, not the actual bottleneck of the engine.
I meant there is no point in going to 51mm if you need to get back to 41 (or 42) mm (for Y or throttle). Unless a 41mm would be introducing high transport losses. A rough calculation gives me a 53m/s air speed per 41mm pipe at 6000rpm on a 2.8L engine, very far from the 340m/s (pessimistic) shock speed, and from 120m/s that are sometimes mentioned as an acceptable high limit for intake systems. So it's better to stay 41mm.
Additionally every sudden change in the section impacts the flow because it creates a sudden change of pressure inside the pipe (which creates wave reflections). Going from I/C to 51mm and then to 41mm (or 42) in Y does introduce losses (unless very smooth transitions were used).
The same calculation of air speed applies to the throttle body: it's not the real bottleneck of the engine. I believe the real bottleneck is elsewhere (to me in the intake ports and valves).
 
F

fphil

Member
Messages
301
goranw said:
I have modified and tuned a friends Ghibli GT 2,8L -96 as much as possible without mechanical modifications of the engine and without anything visible from outside and with all equipment working as normal (AC, instruments and more) and the car should have drivability as a “normal¨ car. The engine was completely overhauled ca 7000 km´s ago. Specification: Fuel pump changed to Walbro 450, Intercoolers changed to QP4, Tubes from Turbo to IC increased from 41mm to 51mm diameter, same as IC inlet and outlet. Same for tubes from IC to manifold. Exhaust front part changed to Tubi with two 100 cell metallic catalysts, one for each side, rear exhaust is custom made 2 1/2” with one small straight through silencer on each side. Turbos are from 3200 Assetto Corsa. Clutch is Sachs Racing. Engine management system is changed to a MaxxEcu Race. The harness from the new ECU to the car was made as a plug-in harness so it attaches to the Cars harness instead of the Weber Marelli ECU´s. We use the car´s standard sensors only added a 60 -2 trigger wheel to pick up the rpm from the crankshaft. The SEM wastegate valve was changed to a MAC valve. Injectors was changed to Bosch EV14 714cc. Ignition modules was changed to fit the new ECU. Weber fuel pressure regulator was changed to one from AEM set to 3,5bar. One Bosch Lambda sensor LSU 4.2 on each side and one K-type temperature sensor in each exhaust manifold. Ethanol sensor so it is now a flex fuel car. The car was mapped and tested on a Dynomite Hub dyno. The car owner wants the engine to behave as much as possible as a NA engine so we held back the turbo pressure at lower RPM and increased it more and more with RPM to get the characteristic he wants. Otherwise, we could have got much higher torque on lower RPM. The results: On 98 Octan standard fuel; 379,2HP @ 6050 RPM (339,3 wheel HP) 514NM @ 4500 RPM (460,3 Wheel NM) max Turbo boost 1,4 bar. With E85 423,6 HP @ 5950 RPM (379,4 Wheel) 553,2 NM @ 4400 RPM (495,5 wheel) max turbo boost 1,5 bar. This was the absolute maximum the engine delivered, higher boost or changed ignition did not give anything more it was totally stop at this power output. Maximum injector opening time at E85 was 83%. The exhaust temp about max allowed 950 deg, almost hitting 1000 deg. With two deg higher (earlier) ignition pinging occurred at top RPM. Higher turbo boost did not give any more power eighter. Our conclusion is, this is the end for the small IHI turbos, they are too small, the turbine is probably to narrow and cannot let more exhaust out.

View attachment 96139
Click to expand...
Thank you for this detailed and much interesting report. Indeed the original rpm from the crank is very noisy especially to regulate at idle. What was the air intake temp? Could we also get the lambda curves for each bank?
 
G

goranw

New Member
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23
Our goal was not to build a race engine, costing a lot of money, our goal was to get as much HP out of the engine as possible by only changing parts outside of the engine. Maybe changing intake ports, valves, camshaft can give moer HP but, as there is nothing to buy it would probably end up to 10-15K EURO +, changing this parts was not our scope. And, it will anyhow be a HP stop because of the turbos. And, you will not find larger turbos that fits exhaust manifolds and downpipes. To overcome this HP bottlenecks it will cost incredibly lot of money.
Again we changed charge pipes to have same dimension out from turbos all the way to the throttle, maybe I remember wrong about throtte diameter, anyhow Y and Thottle has same diameter.
When you choose size of injectors they should not be smaller that 80-90 % open at max, ours was 83% so I think we found the perfect match. And you cannot buy injectors CC by CC there are some sizes availiable, so you have to choose the one nearest your need.
The outside temp was about 5 C deg, we was inside with open doors, guess 15 deg inside, intake temp was over 35 but less than 40. Hard to say exactly as it increases every pull but I would say 38-40. We have a lambda goal of 0.83 but to get rid of pingings and to decrease exhaust temp we need to go down to 0.76. Exhaust temp and back pressure in the exhaust manifolds is the largest problems for performance. And they are connected.
And again absolutely biggest bottleneck for performance (out of the engine as it is) is our small turbos, we think.
 
A

alpa

Member
Messages
185
goranw,
I don't think I have at any moment argued against the validity of the motivation of your work: you said you did not want to change the engine, it's perfectly clear.
The result is very interesting, it shows a quite low performance when compared with many turbo engines of the same period.

My question about the size of injectors was a simple curiosity. I know by experience that when the idle pulse goes under 1ms the idle stability may become an issue.

Bigger RHB5 turbos do exist, or at least have existed.
The Group A FISA document states the following spec for the last GrA biturbo version:
  • 2.5 18v engine, EFI
  • turbo RHB5, turbine steel wheel 43/52mm, compressor aluminum wheel 42/52.5mm.
    Both sets of 3200GT turbo I own have 40mm visible diameter wheels : thus smaller. Assetto Corsa is rated 370hp like any other 3200gt.
  • intake pressure: 2.5 bars (means 1.5 bar boost)
According to what I found on the web these cars were reaching 500-600hp, means turbos were big enough.

The same FISA document states a throttle body 42/42mm. Means 42/42 is enough.

3200GT makes 370hp (390hp according to the owner's manual) with 1 bar boost. You run 1.4 bar and 1000deg exhaust temp and get 380hp. How can this be due to the turbos ?
 
G

goranw

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23
The turbos was picked from a 3200 Assetto Corsa with 32000 km, I know no difference to a normal 3200 but, anyhow they was from a Assetto Corsa.
I do not think you can can find bigger turbos today that really fits to the Maserati, May be 20 years ago there was. It is not enough to be named RHB or RHF they have to start with VM, otherwise they do not fit.
I checked the Y and throttles it is 42mm. 3200 has 0,82 as standard Boost pressure.
Our mission to get as much power as possible out of the 2,8 without mechanical or expensive changes of the engine is not theoretical or scientific proofed it is just reality with results from the bench. We think the turbos is the bottleneck as nothing what ever we do increase power over what was stated, we only get higher exhaust temp and back pressure. Experinced engine tuner says, -to small Turbos. Thats all.
Here is a picture of idle.
 

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G

goranw

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23
One more thing, my friend with a 2,0 Ghibli GT checked his throttles, and they are also 42mm not 44mm.
 
G

goranw

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Messages
23
And, someone probablby will ask why it is such big differnece in temp between L and R side, first it is unfortunately two different temp sensors, one side is 4mm with open end and one is 3mm with closed end. But, when you put some power on the engine they show more or less exactly the same temp.
 
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goranw

New Member
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23
One more thing again, If someone wonders, dont care about the battery voltage, I have loosned the belt from the alternator, I will take the alternator to a alternator repair shop.
 
F456M

F456M

Member
Messages
127
A friend of mine has a 1986 Biturbo Spyder 2,5 liter (origibally carb engine) with some modifications and it delivers 360 hp. I believe he have bigger turbos with the exhaust outlet cover from the 2.24v. the 2,5 origibally had smaller turbos. The car is like a rocket ship! He converted it in 1992 with Electromotive EFI and then later changed to Motec. Much fun with these small twin turbo Maseratis. I just bought a 2,5 injection Spyder project car that I am fixing up. Need to get some more out of that too!! Where can I get a better chip for it?
 

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A

alpa

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185
I guess his Spyder was with late 2L 220hp or 2.8 18v heads. 2.5 turbos where real small and not sure they were water cooled.
You don't need better chips: just move SEM restrictors to the Ghibli position, you'll get 1bar boost instead of 0.8bar. Not sure EFI 2.5 had late heads with two big intake valves. Also find a short 3.73:1 Ranger diff (your 2.5 is 4 bolt I guess so it's a Sensitork).

I'm convinced the 18v heads are almost as good as 24v ones, while they are much cheaper, smaller and lighter. Intake valves are smaller however ports and are larger than on 24v, intake seats are same size as on 24v. I'm currently rebuilding my 2.8 18v (222E) and doing lots of mods: forged pistons (about 8:1CR), bigger unshrouded valves (BMW 30mm), many changes. Stock turbos, they should be enough up to 320-340hp at 1.2 bars with a better mapping (stock ECUs). It's a fun (and expensive) pastime. Also bought the ASMotor struts.
 
A

alpa

Member
Messages
185
Hi goranw,

I'm currently working on a 2.8 18v engine and I comparing many parts I own.
I'd like to warn you about an important issue of the v6 engines: they were NOT made to run high revs neither high boost. They must be first assembled with the right parts.
This may also impact the performance numbers you are observing.

Let me explain about the 24v version, even though the same problems exist with the 18v ones.
The 24v appeared as a 2.0 24v engine which was an evolution of the 18v engine. The 2.24 block is still the 18v one with Cos heads. This means it's still using short conrods and thus quite tall and heavy pistons (all v6 blocks have the same deck height). So 2.24 was rev limited to 6300 rpm. Camshafts were mild: 8.6mm lift on 30mm valves (18v were 9.7 lift on 28.3 valves and larger ports).
Then (I guess) they made the Shamal v8 and realized they could use the same longer and lighter rods on the v6 (this is my vision of the order of events). So they did the Racing and then Ghibli 2.0 24v engines with longer rods and shorter and lighter (forged this time) pistons.
Problem: they did not adjust the heads (not surprising with poor Maserati). Except that on the GT versions they worsen them: they switched from (good) one groove stem valves to (average) three groove stems and std (crappy) locks. So everything else remained the same: chambers, cams, seats, ports, springs, retainers,... Everything.
I invite you to read the specs of the 24v heads. I checked and compared: the data about the springs is correct. And '98 Ghibli GT heads still have the same springs as early 2.24 engines (I have both).
The 2.24 workshop manual says for a pair of springs: 21kg seat pressure, 55kg at 9.5mm lift (while it's actually 8.5mm).
This is theory and this is already a quite low pressure for a boosted and revving engine. 2.24 was running 0.8bars boost level. A rough estimation gives us a valve surface of 1.5x1.5x pi= 7cm2, which gives an air pressure of 0.8 x 7 = 5.6kg at full boost. So the theoretical seat pressure falls down to 15kg and this is a very low number for an engine reaching 6300rpm.
If you open a 24v engine you'll notice many traces of wear on the external valve springs and the low spring retainers. This is an obvious sign of a valve float. The whole rotates and springs touch the pushrods. This is a source of fatigue for the springs. Actually when I measure the spring forces of both 2.24 and GT engines I find much lower numbers: about 15kg and 45kg.
Now what happens when you run a GT engine with a 1.5 bar boost ? The air pressure on the valves reaches 10kg ! They just don't close any more, they constantly bounce at high RPMs.

This is to be added to the fact that intake ports are too narrow compared to the valve size.
 
Last edited:
davy83

davy83

Member
Messages
2,823
alpa said:
Very interesting !

Why to change all the intake pipes if you don't change the Y which is ahead the throttle body ? It's the bottleneck.
714cc is a bit huge for 70hp. Was it easy to set up the idle ? What's the pulse width in idle ?

3200gt make 370hp stock and there is always a margin in the turbo sizing.
My hypothesis is that the engine is limited by too narrow intake ports and small valves, see here:

I wish I could afford a Dynomite Hub dyno
Click to expand...
3200 makes at least 410HP stock. Brochure is not correct, quite a few rolling road tests elsewhere on this forum will testify to this.
 
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