TU3JP cylinderhead swap result!

[totempalen]

In this thread I will be sharing my experience with head swapping my 1.4l TU3JP Saxo.

The result
I went from ~85hp with a (proper)cold air intake and decat to ~105hp after the headswap. From the stock 75hp to 105hp is a 40% gain.
Yellow/green is before the headswap and remap. Blue is afterwards. HP on the left, Nm on the right.



Mods
To achieve 105hp the follow mods were done to the car.
TU5JP cylinderhead (black top)
TU5JP intake manifold + throttle body
TU5JP injectors
piper 4-1 exhaust manifold
GRAMS Racing exhaust
ME221 Gen 2 stand alone ecu. Installed and mapped by Van Drie Performance
Bosch MAP sensor
Bosch 4.2 LSU wideband sensor

Assessment
The interesting question here is ofcourse. Where did I make the gains?
Had we done all the mods except for the head swap, how much power would it have made. A really good question, unfortunately I have no good answer for this. I would like to think the head swap played a big role. But it's hard to say.

Notes
My 1.4 block had a silvertop roller rocker cylinderhead. The 1.6 head is a blacktop solid rocker.
The valve sizes for the 1.4 silvertop are as follows:
Intake: 36.7mm / 36.8mm (I found conflicting info on this)
Exhaust: 29.4mm
Now for the 1.6 blacktop.
Intake: 39.4mm
Exhaust: 31.3mm
Meaning we have a difference of:
Intake: 2.6mm - 2.7mm
Exhaust: 1.9mm

Compression
Unfortunately I did not compression test the engine before doing the headswap, so I have no numbers on this. After the headswap I have done a compression test and got 3 cylinders at ~12bar and 1 cylinder at ~11.5 bar. Keep in mind this is measured compression. This is not representative of the static compression ratio.
I cannot say with certainty what affect this modification has had on the compression ratio.

Parts numbers
Old cylinderhead, TU3JP silvertop from 2000.
0200 AR

New cylinderhead, TU5JP blacktop from 1998
0200 G4

Sealing and size issues
When swapping the 1.6 head on the 1.4 engine block we run into a problem.
The inner bore of the block and head do not match. This results into something like illustrated here:


This picture is exaggerated, but you get the idea. The inner edge of the head mates with the outer edge of the block.
This mismatch leads to a potential for headgasket issues. With the TU3JP being an open deck block, the cylinder wall is all you get. beyond that is coolant. So the (now) thin layer where the outer edge of the block and inner edge of the head meet, is all you get to seal them together.
I personally used an oem 1.6 MLS headgasket and thus far I have not had any issues. I will continue to closely monitor my oil and coolant. This is now definitely a weak link in my engine.


But why?
There's a few different reasons one might do this:
1. Legality
Engine swaps can be a legal hassle in a lot of countries.
2. Ease
Swapping a whole engine can be very daunting for beginners such as myself. Comparatively, swapping a cylinderhead is much easier.
3. Weight
The aluminium open deck 1.4 is significantly lighter than the cast iron closed deck 1.6 blocks.

[SteveG]

It's interesting you have managed to get roughly the same output as a standard 1.6 although I think the TU5JP is quoted as only having 90bhp. I wonder what the output of a 1.6 with a cam and new ECU would be. If I ever get my pistons fitted to my rods I might find out !

[MartinObviously]

You have no clearance issue with the head as you describe, it's the same head as the Rallye and it's on a TU2J2 unit (1.3) with the 39mm and 31mm valve sizes. No mismatch or HG issues will arrive.

You've essentially built a 1.4 Rallye Engine.

Mosts of your power gain comes from the different camshaft profile. Standard 1.4 with the original head can make nearly 100hp by just fitting a sports cam or a "J" cam from a Rallye. The 1.4 cam as standard is a "cool" cam designed purely for fuel efficiency and emissions.