When modifying motorcycles, Harley-Davidson owners are known to be among the most extreme. Keeping that in mind, manufacturers of HD offer stage upgrade kits. Nowadays, stages 3 and stage 4 are the most familiar.
But Harley stage 3 vs. stage 4: which will improve your ride? Stage 4 has better horsepower, air velocity, lift, and a larger carburetor than stage 3. Usually, the stage 4 upgrade will improve the ride over 5000 rpm, which stage 3 can’t do.
To clear out your confusion about which one to choose, we have developed a detailed comparison between these two. After reading this article, you will be able to decide for yourself which better suits your requirements.
Table: Harley Stage 3 vs. Stage 4 Comparison
In this section, we will compare multiple parameters between stage III and stage IV.
| Parameters | Stage 3 | Stage 4 |
|---|---|---|
| Torque | 24% more torque | Same as stage 3 |
| Horsepower | Power upgrades almost 15%-39% | Power upgrades approximately 40%-52% |
| Camshaft | SE8 498 | SE8 515 |
| Airflow | High airflow | High airflow velocity with high airflow |
| Carburetor | Original carburetor mechanism | Larger carburetor mechanism |
| Costing | $1,700-$1,900 without labor costs | $2,200-$3,800 without labor costs |
Harley Stage 3 vs. Stage 4 [In Depth Comparison]
Now, let’s go through the details of these comparisons:
1. Torque
Generally, in the upgrade of stage III and stage IV, there is an additional torque kit for improving the torque. The torque of a stage III bike can improve by around 13%-17%, depending on the engine size.
This torque can even increase up to 24%. On the other hand, the torque kits will increase the torque of the stage IV bike by 24%.
2. Horse Power
In stage III, pistons and huge bore cylinders are added. These provide more space for the valve opening. As a result, it will get more space for air and fuel injection into the engine. This increase in the amount of air-fuel mixture helps to improve horsepower.
The power increment will also depend on the features and size of the bike engine. Here is the list:
| Engine Size | Power Increment |
|---|---|
| 107CI-114CI | 39% |
| 114CI-117CI | 24% |
| 107CI-119CI | 23% |
| 114CI-122CI | 15% |
In the case of the stage IV bikes, you will get more power output than any stage III. Mainly, this stage comes with a throttle body and cylinder head. These parts ensure well-controlled airflow inside the engine. And this better control of air intake improves the horsepower of the engine.
Likewise, this control in the air intake also depends on the size of the engine. Here is the list:
| Engine Size | Power Increment |
|---|---|
| 107CI-114CI | 52% |
| 114CI-117CI | 40% |
3. Camshaft
There is camshaft advancement in both stage III and stage IV. Generally, stage III comes with cam SE8 498, and stage IV comes with SE8 515. There is a difference between their lift performance and the valve opening duration.
The more the lift and duration, the more the engine’s performance will be. When the duration and lift increase, the engine gets more time for air-fuel intake.
The table shows that SE8 515 of stage IV will provide more lift and duration than SE8 498.
Camshafts
Lift
Duration At 0.05
| At Valve Intake | At Valve Exhaust | Intake | Exhaust | |
| SE8 498 | 0.498 inches | 0.491 inches | 209° | 247° |
| SE8 515 | 0.516 inches | 0.513 inches | 227° | 249° |
4. Airflow
In stage III, the higher diameter of the cylinder provides a higher displacement ratio. Thus, the engine will have high airflow as it will intake more air-fuel mixture.
On the other hand, in the stage IV upgrade, there will also be a cylinder head for higher airflow. Also, a smaller size and ported CNC will be inside the aluminum manifold.
While feeding through the manifold, the increased airflow will produce a high air velocity. That means, in stage IV, there will be a high air velocity along with higher airflow.
5. Carburetor
The technical aspects of a stage III engine will depend on the original carburetor mechanism. This original size of the carburetor will provide the optimum level of throttle response and RPM acceleration.
But in the case of stage IV, a larger carburetor mechanism is preferred. The larger size of the carburetor will provide a slower response of the throttle. As a result, it will ensure higher RPM acceleration. Thus, you will get top-end acceleration quality from the stage IV upgrade.
6. Costing
The price range of stage III is lesser than that of stage IV. The stage III kit will cost around $1,700-$1,900. And the stage IV kits will come at $2,200-$3,800 without the installation cost. This installation cost of labor will vary from place to place.
Upgrades In Harley Stage 3 And Stage 4
Stage 3 is an upgraded version of stage 2 and it comes with several additional components for further enhancing efficiency. The working parts in this stage are:
- Bolt-on cylinder
- Intake and exhaust upgrade
- Cylinder of larger bore diameter
- Pistons
- Valve spring
- Lifters
- Cam upgradation
- Gaskets on top ends
- Springs on clutch ends
These performing parts will provide a higher performance range than the earlier stage II bike.
In stage IV, there will be the same components as stage III, with an addition of a throttle body and cylinder heads. These extra parts of this stage help improve the engine’s airflow. But this throttle body is prone to damage very quickly. And this damage may trigger the Harley code p1510.
Which One Is Better? Harley Stage 3 Or Stage 4?
Which one is better mainly depends on the user’s perspective. If you see the Harley stage 3 vs. stage 4 comparison, you can decide which best fits your criteria.
Both come with intake and exhaust upgrades. These upgrades can help solve Harley Davidson Switchback problems by reducing vibration issues.
The comparison discussion clearly shows that the stage IV upgrade will provide better power and performance than stage III. But, the stage 4 kits cost more than the stage 3 upgrade kits.
In that sense, if you are searching for an optimum quality bike within a budget-friendly range, you can go for stage III. But if you don’t want to compromise with the performance, you can choose stage IV.
Which One Will Improve Your Ride Between Harley Stage 3 And Stage 4?
Stage IV can provide better torque, rpm, and hp than stage III. But the torque curve of stage IV is complicated. Because the torque curve of stage III increases linearly and then drops at the end.
On the other hand, the torque of stage IV bikes will increase initially. But after 3000 rpm, the torque will drop and go up again around 5000 rpm.
So, you can only experience the higher torque of stage 4 when you ride the bike at higher rpm. And this isn’t quite the average speed in daily life on the road. So, if you pay for a stage 4 upgrade, it might be a waste of money when you use it daily.
But if you are more into bike racing, stage 4 is to improve your ride. That is because stage 3 won’t provide impressive torque over 3500rpm, but stage 4 bikes will do.
Check this YouTube video to understand the torque discussion better.
FAQs
In this FAQs section, we will answer a few most asked questions about Harley stage 3 and stage 4.
Q: What Could Be The Cheaper Alternative To Harley Stage 3?
A dyno and TTS100 camshaft tune on stage 2 can be a cheaper alternative to stage 3. With this tuning, stage 2 will overcome the missing three cubic inches. Hence, it will provide equivalent performance but be less expensive than stage 3.
Q: Which One is a Better Option For Harley Stage 3 And Stage 4 Between HD117 And FM 128?
Torque from HD117 will be better in stage 3 than stage 4. But FM 128 is a “low compression” and Impress torque-providing build. Also, all of them will cost around $4k-$5k. So, FM 128 will be a better option than HD117.
Q: What Gives The Higher HP In Stage 4?
In stage 4, manufacturers cast the CNC port and turned them more minor than in those earlier stages. As a result, the high air flow from the cylinder head gets higher velocity in stage 4. This upgrade provides higher HP in stage 4.
Conclusion
You should modify your Harley Davidson bike with trustworthy upgrades like stage 3 and stage 4. But before that, you should have an idea about Harley stage 3 vs. stage 4: which one will improve your ride?
Stage 3 is the optimum quality upgrade within the low budget range. Contrarily, stage 4 provides higher performance, but the price range is more elevated. Also, this upgrade serves better torque, only over 5000rpm. Hence, your riding habit and budget range are the primary concerns when choosing the upgrades.