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T04E-50 .63 A/R Turbo = Too laggy?

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Forgive me if this topic was discussed in the past, but I'd like to start a technical conversation about 84-87 (+88USA) turbo replacements/alternatives.


From 1980-88, Lotus used the Garrett T3 turbocharger. It has .63 a/r turbine and .42 a/r compressor, 1.80 turbine inducer, 1.73 compressor inducer

Here is the info, direct from Mr.Esprit :-
The Turbocharger on the USA Turbos with Bosch K Injection (86, 87 & 88)

are Garrett T3, Lotus Part No. C910E6372F (Listed in Lotus Parts Book)
Specification as follows :-
0.63 A/R Turbine, 1.80 turbine inducer,
0.42 Comp,  1.72 compressor inducer
55 Trim Comp Wheel
Boost set at 7psi (remote waste gate with spacer ring) and 9.5psi without the ring


I found this turbo-to-engine sizing chart:
For 2.2 L engine and 300/350HP, the chart suggests T04E-50  stage II .48 A/R or even .63 A/R, which may be to "laggy" .

Have anyone tried this tsize/trim,yet?


Analysis of several Turbo Maps suggested Garrett GT2860RS, 60mm, 62 Trim, 0.60 A/R 

I like this one very much.


FYI:  our 910 engine air flow values are below.


   Press.Ratio PR=  1.48                    PR= 1.68

                               7 psi                           10 psi

3250 rpm              10.54 lbs/min               14.06 lbs/min


7000 rpm              22.60 lbs/min               29.0 lbs/min



Please chime in with the turbo number, type/size/trim and your driving impressions.

On paper things look good, but nothing replaces an empirical data and seat-of-da-pants accelerometer.


Any thoughts or personal impressions?



Edited by MrDangerUS

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Upgrade today to remove Google ads and support TLF.

Here is a nice turbo calculator:

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Hi, the Garrett stuf you mention is fairly old technology,

with new turbine technology which is made for low end torque and a slightly reduced A/R

the transient respone should improve significantly.


As I only know MHI nomenclature and maps, I know a max size TD04HL 58mm compressor

will achieve easlily the flow of 0.29 lbs/min. With a flow limit of approx 39/lbs/min.

Combined with a 7cm turbine, this should be ok for the 300/350 hp. depending on

the aftertreatment. (back pressure)

VAN DER LEE Turbo Systems     -

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The same turbo set-up is used on the Ford Sierra Cosworth and Escort Cosworth (2liter 4cyl. Turbo Engines)

They had 3 different turbine housings 0,48 0,54 & 0,63 to chose from. Also different size compressor housings were available. They were called Garret T34 or T35 turbo (not an official Garrett name)

Google this and a lot of info will pop-up

But I aggree with Plum..., the unit is more than 25yrs old, it is time to cash the improvements in technology.

Edited by bosbon_be

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perhaps  one on my 1.8vtec Honda  revs to 8500 rpm soon 9k-=10:1 CR  will add this copied info.


40 TRIM > 20LB MIN 37.69 60.12
45 TRIM > 23LB MIN (stock cossie) 40.51 60.12
50 TRIM > 27LB MIN 42.52 60.12
55 TRIM > 44.70 60.12
60 TRIM > 32LB MIN 46.48 60.12
60 TRIM > 36LB MIN (super 60) 48.26 60.12

ALL T3 TURBINES = MINOR > 48.21 MAJOR > 58.90
STAGE 2 TURBINE = MINOR > 53.90 MAJOR > 65.00
STAGE 3 TURBINE = MINOR > 56.62 MAJOR > 65.00


example ... stock cossie 2wd = 42 comp / 48 exh


T03/T04 often called t34 or even t35 --- IS A T3 TURBINE COUPLED TO A T4 COMPRESSOR


S TRIM > 37LB MIN 48.36 69.85
V TRIM > 48LB MIN 55.37 69.85
H TRIM > 49LB MIN 58.37 69.85



example .... stock cossie 4wd = s trim/46 60 comp / 48 exh

good for 360hp on 48 a/r exh housing
390hp on 63 a/r exh housing


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My reading found this,john has done some past homework. :smoke:


Not any more.


Lotusbuzz all gone. :tumbleweed:

All we know is that when they stop making this, we will be properly, properly sad.Jeremy Clarkson on the Esprit.

Opinions are like armpits. Everyone has them, some just stink more than others.

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On all turbo cars equipped with an external wastegate,

the OE turbocharger-to-downpipe adapter creates a severe flow restriction.

The inner "trough" pipe ID is only 1.9" and can not be machined bigger.

Any modern T3 turbine port measures 2.3" ID.

Therefore, a new adapter has to be fabricated to accomodate any turbo upgrade.

Has anyone done this, yet?

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CT3-5356 could be used in place of the old OE "5046"

Tiple ball bearings make it come up at 2000rpm

Modern technology

Very nice

Edited by MrDangerUS

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How did you select the turbo,

did comp turbo provided the maps? Would be interesting to see. As It looks like they have their own billet wheels.


Then for your adaptor, SS 310, should be good. But check the materal of the turbine housing and manifold as well,

as to large expansion properties can lead to gas leakage.

VAN DER LEE Turbo Systems     -

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I just got my car on the road with it's new turbo and Megasquirt MS3X efi. 


The turbo is a turbonetics T3/04E with a .48 AR. IMHO you would probably not be happy with the lag from a .60 AR. I don't know what your HP goal is, but the .48 will allow for the better part of 400HP 


The .48 allows it to spool pretty quick, at least as fast as the factory setup but the car is a blast! I'm having issues getting the boost controlled unfortunately , but am more than satisfied with the turbo choice. Admittedly the tires are old and hard, but when allowed to build boost without control it easily spins the tires in 2nd gear when it come on the boost.   


FWIW I went with an internal style 3 inch ultimate wastegate from ATP, a mandrel bent 3 inch exhaust and a Dynomax 12 inch high flow muffler. The result is a great sound and performance, but it now has boost creep. The turbo makes 15+ lbs of boost with the internal wastegate wide open! It builds slower with the gate wide open but still builds so it needs to be addressed. After reading as much as I could find, it looks like porting the wastegate may be an option but an external wastegate is the only sure way of fixing the problem. As a result, if you plan to use a larger turbo and high flow exhaust, go with an external wastegate from the start and save yourself some problems.   


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Selection trough trial and error.

Friend of mine had 5356 installed on his car for a year. It worked fine despite the wrong compressor wheel sizing. CT has rebuilt his turbo under the warranty. He is porting the cylinder head an should have his car up and running again in spring. I'll keep you posted.

No, CT does not release their maps, no idea why. They have a good product, but they are very secretive.

I understand their motvation, though. I have seen a couple of smaller Turbo Builder companies going bankrupt because an influx of cheap chinese imitations.

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Congrats for the project WELL DONE!

Please post details of your conversion. Make a new dedicated thread!

I see Chevy COP-s and vernier pulleys there. We talking something seriously BAD-A55 !

Perhaps you can adjust the MOPs to help fighting your boost creep?

P.S. With all that power, I hope you've replaced the circlip and differential carrier bearings in your C35 tranny.

Edited by MrDangerUS

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Some engines where boost is increased to the compressor maps surge limit, the wastegate never opens. Typically a properly sized turbo should flow at least 300 cfm more than what the engine will be ingesting.


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