Performance modifications — engine tunes, aftermarket exhausts, suspension upgrades, forced induction — are considered risk-raising by most standard insurers. Non-disclosure is the biggest mistake: if your car has undisclosed performance mods and you have a crash, the insurer can dispute or deny your claim. Expect premium increases of 10–50% depending on the modification type and insurer. Specialist modified-car insurers (including Hagerty and certain non-standard carriers) offer fairer agreed-value pricing for heavily modified vehicles.
Performance modification insurance impact
| Modification | Insurance risk classification | Likely premium effect | Disclosure required? |
|---|---|---|---|
| Aftermarket exhaust (catback only) | Low risk — cosmetic/sound | Minimal (0–5%) | Yes — still disclose |
| ECU remap / tune | Moderate — raises power output | +15–30% on collision | Yes — critical |
| Cold air intake | Low-moderate | Minimal | Yes |
| Suspension lowering | Moderate — changes handling/ride | +10–20% | Yes |
| Turbo / supercharger addition | High — significant power increase | +30–50%+ | Yes — may need specialist policy |
| Track prep / roll cage | High — indicates track use | May void standard policy | Yes — get motorsport cover |
Why performance mods raise your insurance rate
Insurers price risk based on the likelihood and severity of a claim. Performance modifications increase both: a remapped engine with 80 extra horsepower accelerates harder, reaches higher speeds and is statistically more likely to be involved in a speed-related incident. Aftermarket exhausts may suggest a performance-oriented driver. Lowered suspension alters handling characteristics in ways an insurer can't easily model.
This doesn't mean you can't insure a modified car — tens of thousands of modified vehicles are insured every day. It means you have to do it properly.
The non-disclosure problem
Many drivers modify their cars and don't tell their insurer, assuming the modification isn't relevant or wanting to avoid a premium increase. This is one of the more dangerous gambles in consumer insurance. If you have an accident and your insurer discovers undisclosed performance modifications during the claims investigation — which they often do, through inspection, telematics data or CARFAX records — they have grounds to:
- Reduce your claim payout on the basis that the risk was not what you described.
- Deny your claim entirely if the modification is deemed material to the loss.
- Cancel your policy.
- Potentially flag you for fraud if the concealment appears deliberate.
The premium increase for disclosing a catback exhaust is usually minimal; the cost of a denied claim is not.
Exhaust modifications: the range of risk
Not all exhaust modifications are treated equally. A cosmetic catback replacement (replacing the rear section with a louder unit but not changing the engine's power output or emissions controls) is generally viewed as low risk. At the other end of the scale, a full decat (removing catalytic converters) may create legal issues around emissions compliance in your state, and combined with an ECU remap it signals performance intent that most standard insurers will surcharge heavily.
ECU remaps and tuning: the insurer's biggest concern
Engine management remaps are the modification that most concerns standard insurers, because they directly and measurably increase power output. A Stage 1 remap on a turbocharged petrol car might add 50–100 horsepower — changing the vehicle's performance characteristics substantially. Insurers who discover a non-disclosed remap after a claim will routinely investigate whether the increased performance contributed to the incident.
If you have a remapped car, your options are:
- Disclose to your current insurer and accept the surcharge.
- Shop among specialist modified-car insurers who understand remaps and can offer fairer agreed-value pricing.
- Check whether a telematics-based policy (where your actual driving behaviour is rated) might offset the modification surcharge through demonstrably safe driving.
Track days and motorsport use
Standard auto insurance does not cover track use. If your modifications include roll cages, harnesses, fire suppression or anything else indicating circuit racing or autocross participation, you need a separate motorsport or track-day policy for any time the car is on a closed circuit. Personal accident policies for track days are also worth considering, as standard health insurance may exclude racing-related injuries.
If your car is significantly modified, mainstream carriers often can't price it well and may simply decline. Specialist modified-car insurers — including Hagerty (focused on enthusiast vehicles), certain Lloyds-backed markets, and carriers like American Collectors — offer agreed-value policies tailored to modified vehicles, including higher limits for modification spend and coverage that reflects what the car is actually worth rather than a stock depreciation schedule.
Frequently asked questions
Do I have to tell my insurer about an aftermarket exhaust?
Will an ECU remap invalidate my insurance?
Can I get insurance on a heavily modified car?
Is a modified car covered on track?
How much will performance mods raise my premium?
Sources & further reading
Figures, prices and policy details were current at the last-updated date above. Automotive pricing, incentives and regulations change frequently — verify time-sensitive details with the linked primary sources. Read our editorial policy and fact-checking standards.
